Messages in this thread | | | Date | Tue, 10 Aug 2010 10:17:34 +0530 | From | Nitin Gupta <> | Subject | Re: [PATCH 04/10] Use percpu buffers |
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On 08/10/2010 12:27 AM, Pekka Enberg wrote: > On Mon, Aug 9, 2010 at 8:26 PM, Nitin Gupta <ngupta@vflare.org> wrote: >> @@ -303,38 +307,41 @@ static int zram_write(struct zram *zram, struct bio *bio) >> zram_test_flag(zram, index, ZRAM_ZERO)) >> zram_free_page(zram, index); >> >> - mutex_lock(&zram->lock); >> + preempt_disable(); >> + zbuffer = __get_cpu_var(compress_buffer); >> + zworkmem = __get_cpu_var(compress_workmem); >> + if (unlikely(!zbuffer || !zworkmem)) { >> + preempt_enable(); >> + goto out; >> + } > > The per-CPU buffer thing with this preempt_disable() trickery looks > overkill to me. Most block device drivers seem to use mempool_alloc() > for this sort of thing. Is there some reason you can't use that here? >
Other block drivers are allocating relatively small structs using mempool_alloc(). However, in case of zram, these buffers are quite large (compress_workmem is 64K!). So, allocating them on every write would probably be much slower than using a pre-allocated per-cpu buffer.
Thanks, Nitin
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