Messages in this thread | | | Date | Tue, 12 Aug 2014 16:37:40 +0900 | From | Minchan Kim <> | Subject | Re: [PATCH] zram: fix incorrectly stat with failed_reads |
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On Mon, Aug 11, 2014 at 04:39:17PM +0800, Chao Yu wrote: > Since we allocate a temporary buffer in zram_bvec_read to handle partial page > operations in this commit 924bd88d703e53d30f393fac6117f8f1bc79aab6 (Staging: > zram: allow partial page operations), our ->failed_reads value may be incorrect > as we do not increase its value when failed to allocate the temporary buffer. > > Let's fix this issue and correct the annotation of failed_reads.
Good catch. Just out of curiosity.
Did you catch it by code review or real workload?
> > Signed-off-by: Chao Yu <chao2.yu@samsung.com> > --- > drivers/block/zram/zram_drv.c | 1 + > drivers/block/zram/zram_drv.h | 2 +- > 2 files changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index dfa4024..bf8ea1b 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -413,6 +413,7 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, > > if (!uncmem) { > pr_info("Unable to allocate temp memory\n"); > + atomic64_inc(&zram->stats.failed_reads); > ret = -ENOMEM; > goto out_cleanup; > } > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h > index 5b0afde..e0f725c 100644 > --- a/drivers/block/zram/zram_drv.h > +++ b/drivers/block/zram/zram_drv.h > @@ -84,7 +84,7 @@ struct zram_stats { > atomic64_t compr_data_size; /* compressed size of pages stored */ > atomic64_t num_reads; /* failed + successful */ > atomic64_t num_writes; /* --do-- */ > - atomic64_t failed_reads; /* should NEVER! happen */ > + atomic64_t failed_reads; /* can happen when memory is too low */ > 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 */ > -- > 2.0.1.474.g72c7794
How abouting moving failed_reads/writes in zram_bvec_rw?
int zram_bvec_rw(..) { if (rw == READ) { atomic64_inc(num_reads); ret = zram_bvec_read(xxx); } else { atomic64_inc(&num_writes); ret = zram_bvec_write(xxx); }
if (unlikely(ret)) { if (rw == READ) atomic64_inc(failed_reads); else atomic64_inc(failed_writes); } }
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-- Kind regards, Minchan Kim
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