zram: use atomic operation for stat

Some of fields in zram->stats are protected by zram->lock which is
rather coarse-grained so let's use atomic operation without explict
locking.

This patch is ready for removing dependency of zram->lock in read path
which is very coarse-grained rw_semaphore.  Of course, this patch adds
new atomic operation so it might make slow but my 12CPU test couldn't
spot any regression.  All gain/lose is marginal within stddev.

  iozone -t -T -l 12 -u 12 -r 16K -s 60M -I +Z -V 0

  ==Initial write                ==Initial write
  records: 50                    records: 50
  avg:  412875.17                avg:  415638.23
  std:   38543.12 (9.34%)        std:   36601.11 (8.81%)
  max:  521262.03                max:  502976.72
  min:  343263.13                min:  351389.12
  ==Rewrite                      ==Rewrite
  records: 50                    records: 50
  avg:  416640.34                avg:  397914.33
  std:   60798.92 (14.59%)       std:   46150.42 (11.60%)
  max:  543057.07                max:  522669.17
  min:  304071.67                min:  316588.77
  ==Read                         ==Read
  records: 50                    records: 50
  avg: 4147338.63                avg: 4070736.51
  std:  179333.25 (4.32%)        std:  223499.89 (5.49%)
  max: 4459295.28                max: 4539514.44
  min: 3753057.53                min: 3444686.31
  ==Re-read                      ==Re-read
  records: 50                    records: 50
  avg: 4096706.71                avg: 4117218.57
  std:  229735.04 (5.61%)        std:  171676.25 (4.17%)
  max: 4430012.09                max: 4459263.94
  min: 2987217.80                min: 3666904.28
  ==Reverse Read                 ==Reverse Read
  records: 50                    records: 50
  avg: 4062763.83                avg: 4078508.32
  std:  186208.46 (4.58%)        std:  172684.34 (4.23%)
  max: 4401358.78                max: 4424757.22
  min: 3381625.00                min: 3679359.94
  ==Stride read                  ==Stride read
  records: 50                    records: 50
  avg: 4094933.49                avg: 4082170.22
  std:  185710.52 (4.54%)        std:  196346.68 (4.81%)
  max: 4478241.25                max: 4460060.97
  min: 3732593.23                min: 3584125.78
  ==Random read                  ==Random read
  records: 50                    records: 50
  avg: 4031070.04                avg: 4074847.49
  std:  192065.51 (4.76%)        std:  206911.33 (5.08%)
  max: 4356931.16                max: 4399442.56
  min: 3481619.62                min: 3548372.44
  ==Mixed workload               ==Mixed workload
  records: 50                    records: 50
  avg:  149925.73                avg:  149675.54
  std:    7701.26 (5.14%)        std:    6902.09 (4.61%)
  max:  191301.56                max:  175162.05
  min:  133566.28                min:  137762.87
  ==Random write                 ==Random write
  records: 50                    records: 50
  avg:  404050.11                avg:  393021.47
  std:   58887.57 (14.57%)       std:   42813.70 (10.89%)
  max:  601798.09                max:  524533.43
  min:  325176.99                min:  313255.34
  ==Pwrite                       ==Pwrite
  records: 50                    records: 50
  avg:  411217.70                avg:  411237.96
  std:   43114.99 (10.48%)       std:   33136.29 (8.06%)
  max:  530766.79                max:  471899.76
  min:  320786.84                min:  317906.94
  ==Pread                        ==Pread
  records: 50                    records: 50
  avg: 4154908.65                avg: 4087121.92
  std:  151272.08 (3.64%)        std:  219505.04 (5.37%)
  max: 4459478.12                max: 4435857.38
  min: 3730512.41                min: 3101101.67

Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Tested-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Minchan Kim 2014-01-30 15:46:02 -08:00 committed by Linus Torvalds
parent 874e3cddc3
commit deb0bdeb2f
2 changed files with 16 additions and 20 deletions

View File

@ -104,7 +104,7 @@ static ssize_t zero_pages_show(struct device *dev,
{
struct zram *zram = dev_to_zram(dev);
return sprintf(buf, "%u\n", zram->stats.pages_zero);
return sprintf(buf, "%u\n", atomic_read(&zram->stats.pages_zero));
}
static ssize_t orig_data_size_show(struct device *dev,
@ -113,7 +113,7 @@ static ssize_t orig_data_size_show(struct device *dev,
struct zram *zram = dev_to_zram(dev);
return sprintf(buf, "%llu\n",
(u64)(zram->stats.pages_stored) << PAGE_SHIFT);
(u64)(atomic_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
}
static ssize_t compr_data_size_show(struct device *dev,
@ -293,21 +293,21 @@ static void zram_free_page(struct zram *zram, size_t index)
*/
if (zram_test_flag(meta, index, ZRAM_ZERO)) {
zram_clear_flag(meta, index, ZRAM_ZERO);
zram->stats.pages_zero--;
atomic_dec(&zram->stats.pages_zero);
}
return;
}
if (unlikely(size > max_zpage_size))
zram->stats.bad_compress--;
atomic_dec(&zram->stats.bad_compress);
zs_free(meta->mem_pool, handle);
if (size <= PAGE_SIZE / 2)
zram->stats.good_compress--;
atomic_dec(&zram->stats.good_compress);
atomic64_sub(meta->table[index].size, &zram->stats.compr_size);
zram->stats.pages_stored--;
atomic_dec(&zram->stats.pages_stored);
meta->table[index].handle = 0;
meta->table[index].size = 0;
@ -435,7 +435,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
/* Free memory associated with this sector now. */
zram_free_page(zram, index);
zram->stats.pages_zero++;
atomic_inc(&zram->stats.pages_zero);
zram_set_flag(meta, index, ZRAM_ZERO);
ret = 0;
goto out;
@ -456,7 +456,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
}
if (unlikely(clen > max_zpage_size)) {
zram->stats.bad_compress++;
atomic_inc(&zram->stats.bad_compress);
clen = PAGE_SIZE;
src = NULL;
if (is_partial_io(bvec))
@ -493,9 +493,9 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
/* Update stats */
atomic64_add(clen, &zram->stats.compr_size);
zram->stats.pages_stored++;
atomic_inc(&zram->stats.pages_stored);
if (clen <= PAGE_SIZE / 2)
zram->stats.good_compress++;
atomic_inc(&zram->stats.good_compress);
out:
if (is_partial_io(bvec))

View File

@ -68,10 +68,6 @@ struct table {
u8 flags;
} __aligned(4);
/*
* All 64bit fields should only be manipulated by 64bit atomic accessors.
* All modifications to 32bit counter should be protected by zram->lock.
*/
struct zram_stats {
atomic64_t compr_size; /* compressed size of pages stored */
atomic64_t num_reads; /* failed + successful */
@ -80,10 +76,10 @@ struct zram_stats {
atomic64_t failed_writes; /* can happen when memory is too low */
atomic64_t invalid_io; /* non-page-aligned I/O requests */
atomic64_t notify_free; /* no. of swap slot free notifications */
u32 pages_zero; /* no. of zero filled pages */
u32 pages_stored; /* no. of pages currently stored */
u32 good_compress; /* % of pages with compression ratio<=50% */
u32 bad_compress; /* % of pages with compression ratio>=75% */
atomic_t pages_zero; /* no. of zero filled pages */
atomic_t pages_stored; /* no. of pages currently stored */
atomic_t good_compress; /* % of pages with compression ratio<=50% */
atomic_t bad_compress; /* % of pages with compression ratio>=75% */
};
struct zram_meta {
@ -101,8 +97,8 @@ struct zram_slot_free {
struct zram {
struct zram_meta *meta;
struct rw_semaphore lock; /* protect compression buffers, table,
* 32bit stat counters against concurrent
* notifications, reads and writes */
* reads and writes
*/
struct work_struct free_work; /* handle pending free request */
struct zram_slot_free *slot_free_rq; /* list head of free request */