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![David Chinner](/assets/img/avatar_default.png)
Now that the ktrace_enter() code is using atomics, the non-power-of-2 buffer sizes - which require modulus operations to get the index - are showing up as using substantial CPU in the profiles. Force the buffer sizes to be rounded up to the nearest power of two and use masking rather than modulus operations to convert the index counter to the buffer index. This reduces ktrace_enter overhead to 8% of a CPU time, and again almost halves the trace intensive test runtime. SGI-PV: 977546 SGI-Modid: xfs-linux-melb:xfs-kern:30538a Signed-off-by: David Chinner <dgc@sgi.com> Signed-off-by: Christoph Hellwig <hch@infradead.org> Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>
328 lines
7.3 KiB
C
328 lines
7.3 KiB
C
/*
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* Copyright (c) 2000-2003,2005 Silicon Graphics, Inc.
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* All Rights Reserved.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it would be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <xfs.h>
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static kmem_zone_t *ktrace_hdr_zone;
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static kmem_zone_t *ktrace_ent_zone;
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static int ktrace_zentries;
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void __init
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ktrace_init(int zentries)
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{
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ktrace_zentries = roundup_pow_of_two(zentries);
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ktrace_hdr_zone = kmem_zone_init(sizeof(ktrace_t),
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"ktrace_hdr");
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ASSERT(ktrace_hdr_zone);
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ktrace_ent_zone = kmem_zone_init(ktrace_zentries
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* sizeof(ktrace_entry_t),
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"ktrace_ent");
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ASSERT(ktrace_ent_zone);
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}
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void __exit
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ktrace_uninit(void)
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{
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kmem_zone_destroy(ktrace_hdr_zone);
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kmem_zone_destroy(ktrace_ent_zone);
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}
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/*
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* ktrace_alloc()
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*
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* Allocate a ktrace header and enough buffering for the given
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* number of entries. Round the number of entries up to a
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* power of 2 so we can do fast masking to get the index from
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* the atomic index counter.
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*/
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ktrace_t *
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ktrace_alloc(int nentries, unsigned int __nocast sleep)
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{
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ktrace_t *ktp;
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ktrace_entry_t *ktep;
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int entries;
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ktp = (ktrace_t*)kmem_zone_alloc(ktrace_hdr_zone, sleep);
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if (ktp == (ktrace_t*)NULL) {
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/*
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* KM_SLEEP callers don't expect failure.
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*/
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if (sleep & KM_SLEEP)
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panic("ktrace_alloc: NULL memory on KM_SLEEP request!");
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return NULL;
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}
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/*
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* Special treatment for buffers with the ktrace_zentries entries
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*/
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entries = roundup_pow_of_two(nentries);
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if (entries == ktrace_zentries) {
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ktep = (ktrace_entry_t*)kmem_zone_zalloc(ktrace_ent_zone,
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sleep);
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} else {
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ktep = (ktrace_entry_t*)kmem_zalloc((entries * sizeof(*ktep)),
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sleep | KM_LARGE);
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}
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if (ktep == NULL) {
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/*
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* KM_SLEEP callers don't expect failure.
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*/
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if (sleep & KM_SLEEP)
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panic("ktrace_alloc: NULL memory on KM_SLEEP request!");
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kmem_free(ktp, sizeof(*ktp));
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return NULL;
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}
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ktp->kt_entries = ktep;
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ktp->kt_nentries = entries;
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ASSERT(is_power_of_2(entries));
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ktp->kt_index_mask = entries - 1;
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atomic_set(&ktp->kt_index, 0);
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ktp->kt_rollover = 0;
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return ktp;
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}
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/*
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* ktrace_free()
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*
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* Free up the ktrace header and buffer. It is up to the caller
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* to ensure that no-one is referencing it.
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*/
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void
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ktrace_free(ktrace_t *ktp)
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{
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int entries_size;
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if (ktp == (ktrace_t *)NULL)
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return;
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/*
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* Special treatment for the Vnode trace buffer.
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*/
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if (ktp->kt_nentries == ktrace_zentries) {
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kmem_zone_free(ktrace_ent_zone, ktp->kt_entries);
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} else {
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entries_size = (int)(ktp->kt_nentries * sizeof(ktrace_entry_t));
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kmem_free(ktp->kt_entries, entries_size);
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}
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kmem_zone_free(ktrace_hdr_zone, ktp);
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}
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/*
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* Enter the given values into the "next" entry in the trace buffer.
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* kt_index is always the index of the next entry to be filled.
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*/
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void
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ktrace_enter(
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ktrace_t *ktp,
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void *val0,
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void *val1,
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void *val2,
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void *val3,
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void *val4,
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void *val5,
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void *val6,
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void *val7,
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void *val8,
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void *val9,
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void *val10,
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void *val11,
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void *val12,
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void *val13,
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void *val14,
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void *val15)
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{
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int index;
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ktrace_entry_t *ktep;
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ASSERT(ktp != NULL);
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/*
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* Grab an entry by pushing the index up to the next one.
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*/
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index = atomic_add_return(1, &ktp->kt_index);
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index = (index - 1) & ktp->kt_index_mask;
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if (!ktp->kt_rollover && index == ktp->kt_nentries - 1)
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ktp->kt_rollover = 1;
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ASSERT((index >= 0) && (index < ktp->kt_nentries));
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ktep = &(ktp->kt_entries[index]);
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ktep->val[0] = val0;
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ktep->val[1] = val1;
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ktep->val[2] = val2;
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ktep->val[3] = val3;
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ktep->val[4] = val4;
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ktep->val[5] = val5;
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ktep->val[6] = val6;
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ktep->val[7] = val7;
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ktep->val[8] = val8;
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ktep->val[9] = val9;
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ktep->val[10] = val10;
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ktep->val[11] = val11;
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ktep->val[12] = val12;
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ktep->val[13] = val13;
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ktep->val[14] = val14;
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ktep->val[15] = val15;
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}
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/*
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* Return the number of entries in the trace buffer.
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*/
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int
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ktrace_nentries(
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ktrace_t *ktp)
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{
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int index;
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if (ktp == NULL)
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return 0;
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index = atomic_read(&ktp->kt_index) & ktp->kt_index_mask;
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return (ktp->kt_rollover ? ktp->kt_nentries : index);
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}
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/*
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* ktrace_first()
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*
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* This is used to find the start of the trace buffer.
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* In conjunction with ktrace_next() it can be used to
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* iterate through the entire trace buffer. This code does
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* not do any locking because it is assumed that it is called
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* from the debugger.
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*
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* The caller must pass in a pointer to a ktrace_snap
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* structure in which we will keep some state used to
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* iterate through the buffer. This state must not touched
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* by any code outside of this module.
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*/
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ktrace_entry_t *
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ktrace_first(ktrace_t *ktp, ktrace_snap_t *ktsp)
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{
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ktrace_entry_t *ktep;
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int index;
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int nentries;
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if (ktp->kt_rollover)
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index = atomic_read(&ktp->kt_index) & ktp->kt_index_mask;
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else
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index = 0;
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ktsp->ks_start = index;
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ktep = &(ktp->kt_entries[index]);
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nentries = ktrace_nentries(ktp);
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index++;
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if (index < nentries) {
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ktsp->ks_index = index;
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} else {
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ktsp->ks_index = 0;
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if (index > nentries)
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ktep = NULL;
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}
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return ktep;
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}
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/*
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* ktrace_next()
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*
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* This is used to iterate through the entries of the given
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* trace buffer. The caller must pass in the ktrace_snap_t
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* structure initialized by ktrace_first(). The return value
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* will be either a pointer to the next ktrace_entry or NULL
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* if all of the entries have been traversed.
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*/
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ktrace_entry_t *
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ktrace_next(
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ktrace_t *ktp,
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ktrace_snap_t *ktsp)
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{
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int index;
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ktrace_entry_t *ktep;
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index = ktsp->ks_index;
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if (index == ktsp->ks_start) {
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ktep = NULL;
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} else {
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ktep = &ktp->kt_entries[index];
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}
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index++;
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if (index == ktrace_nentries(ktp)) {
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ktsp->ks_index = 0;
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} else {
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ktsp->ks_index = index;
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}
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return ktep;
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}
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/*
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* ktrace_skip()
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*
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* Skip the next "count" entries and return the entry after that.
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* Return NULL if this causes us to iterate past the beginning again.
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*/
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ktrace_entry_t *
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ktrace_skip(
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ktrace_t *ktp,
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int count,
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ktrace_snap_t *ktsp)
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{
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int index;
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int new_index;
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ktrace_entry_t *ktep;
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int nentries = ktrace_nentries(ktp);
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index = ktsp->ks_index;
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new_index = index + count;
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while (new_index >= nentries) {
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new_index -= nentries;
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}
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if (index == ktsp->ks_start) {
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/*
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* We've iterated around to the start, so we're done.
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*/
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ktep = NULL;
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} else if ((new_index < index) && (index < ktsp->ks_index)) {
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/*
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* We've skipped past the start again, so we're done.
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*/
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ktep = NULL;
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ktsp->ks_index = ktsp->ks_start;
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} else {
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ktep = &(ktp->kt_entries[new_index]);
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new_index++;
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if (new_index == nentries) {
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ktsp->ks_index = 0;
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} else {
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ktsp->ks_index = new_index;
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}
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}
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return ktep;
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}
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