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author | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 06:49:19 (GMT) |
---|---|---|
committer | Nick Piggin <npiggin@kernel.dk> | 2011-01-07 06:50:17 (GMT) |
commit | 3e880fb5e4bb6a012035e3edd0586ee2817c2e24 (patch) | |
tree | 665101c2c559c26e2dff2c7eca2c747fb736b524 /fs/dcache.c | |
parent | 86c8749ede0c59e590de9267066932a26f1ce796 (diff) | |
download | linux-fsl-qoriq-3e880fb5e4bb6a012035e3edd0586ee2817c2e24.tar.xz |
fs: use fast counters for vfs caches
percpu_counter library generates quite nasty code, so unless you need
to dynamically allocate counters or take fast approximate value, a
simple per cpu set of counters is much better.
The percpu_counter can never be made to work as well, because it has an
indirection from pointer to percpu memory, and it can't use direct
this_cpu_inc interfaces because it doesn't use static PER_CPU data, so
code will always be worse.
In the fastpath, it is the difference between this:
incl %gs:nr_dentry # nr_dentry
and this:
movl percpu_counter_batch(%rip), %edx # percpu_counter_batch,
movl $1, %esi #,
movq $nr_dentry, %rdi #,
call __percpu_counter_add # (plus I clobber registers)
__percpu_counter_add:
pushq %rbp #
movq %rsp, %rbp #,
subq $32, %rsp #,
movq %rbx, -24(%rbp) #,
movq %r12, -16(%rbp) #,
movq %r13, -8(%rbp) #,
movq %rdi, %rbx # fbc, fbc
#APP
# 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1
movq %gs:kernel_stack,%rax #, pfo_ret__
# 0 "" 2
#NO_APP
incl -8124(%rax) # <variable>.preempt_count
movq 32(%rdi), %r12 # <variable>.counters, tcp_ptr__
#APP
# 78 "lib/percpu_counter.c" 1
add %gs:this_cpu_off, %r12 # this_cpu_off, tcp_ptr__
# 0 "" 2
#NO_APP
movslq (%r12),%r13 #* tcp_ptr__, tmp73
movslq %edx,%rax # batch, batch
addq %rsi, %r13 # amount, count
cmpq %rax, %r13 # batch, count
jge .L27 #,
negl %edx # tmp76
movslq %edx,%rdx # tmp76, tmp77
cmpq %rdx, %r13 # tmp77, count
jg .L28 #,
.L27:
movq %rbx, %rdi # fbc,
call _raw_spin_lock #
addq %r13, 8(%rbx) # count, <variable>.count
movq %rbx, %rdi # fbc,
movl $0, (%r12) #,* tcp_ptr__
call _raw_spin_unlock #
.L29:
#APP
# 216 "/home/npiggin/usr/src/linux-2.6/arch/x86/include/asm/thread_info.h" 1
movq %gs:kernel_stack,%rax #, pfo_ret__
# 0 "" 2
#NO_APP
decl -8124(%rax) # <variable>.preempt_count
movq -8136(%rax), %rax #, D.14625
testb $8, %al #, D.14625
jne .L32 #,
.L31:
movq -24(%rbp), %rbx #,
movq -16(%rbp), %r12 #,
movq -8(%rbp), %r13 #,
leave
ret
.p2align 4,,10
.p2align 3
.L28:
movl %r13d, (%r12) # count,*
jmp .L29 #
.L32:
call preempt_schedule #
.p2align 4,,6
jmp .L31 #
.size __percpu_counter_add, .-__percpu_counter_add
.p2align 4,,15
Signed-off-by: Nick Piggin <npiggin@kernel.dk>
Diffstat (limited to 'fs/dcache.c')
-rw-r--r-- | fs/dcache.c | 19 |
1 files changed, 13 insertions, 6 deletions
diff --git a/fs/dcache.c b/fs/dcache.c index f62ba90..b2cb266 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -67,13 +67,22 @@ struct dentry_stat_t dentry_stat = { .age_limit = 45, }; -static struct percpu_counter nr_dentry __cacheline_aligned_in_smp; +static DEFINE_PER_CPU(unsigned int, nr_dentry); #if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS) +static int get_nr_dentry(void) +{ + int i; + int sum = 0; + for_each_possible_cpu(i) + sum += per_cpu(nr_dentry, i); + return sum < 0 ? 0 : sum; +} + int proc_nr_dentry(ctl_table *table, int write, void __user *buffer, size_t *lenp, loff_t *ppos) { - dentry_stat.nr_dentry = percpu_counter_sum_positive(&nr_dentry); + dentry_stat.nr_dentry = get_nr_dentry(); return proc_dointvec(table, write, buffer, lenp, ppos); } #endif @@ -93,7 +102,7 @@ static void __d_free(struct rcu_head *head) */ static void d_free(struct dentry *dentry) { - percpu_counter_dec(&nr_dentry); + this_cpu_dec(nr_dentry); if (dentry->d_op && dentry->d_op->d_release) dentry->d_op->d_release(dentry); @@ -981,7 +990,7 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) list_add(&dentry->d_u.d_child, &parent->d_subdirs); spin_unlock(&dcache_lock); - percpu_counter_inc(&nr_dentry); + this_cpu_inc(nr_dentry); return dentry; } @@ -2418,8 +2427,6 @@ static void __init dcache_init(void) { int loop; - percpu_counter_init(&nr_dentry, 0); - /* * A constructor could be added for stable state like the lists, * but it is probably not worth it because of the cache nature |