> -----Original Message-----
> From: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
> Sent: Thursday, February 6, 2025 11:11 AM
> To: Sridhar, Kanchana P <kanchana.p.sridhar@xxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-mm@xxxxxxxxx;
> hannes@xxxxxxxxxxx; nphamcs@xxxxxxxxx; chengming.zhou@xxxxxxxxx;
> usamaarif642@xxxxxxxxx; ryan.roberts@xxxxxxx; 21cnbao@xxxxxxxxx;
> akpm@xxxxxxxxxxxxxxxxxxxx; linux-crypto@xxxxxxxxxxxxxxx;
> herbert@xxxxxxxxxxxxxxxxxxx; davem@xxxxxxxxxxxxx;
> clabbe@xxxxxxxxxxxx; ardb@xxxxxxxxxx; ebiggers@xxxxxxxxxx;
> surenb@xxxxxxxxxx; Accardi, Kristen C <kristen.c.accardi@xxxxxxxxx>;
> Feghali, Wajdi K <wajdi.k.feghali@xxxxxxxxx>; Gopal, Vinodh
> <vinodh.gopal@xxxxxxxxx>
> Subject: Re: [PATCH v6 15/16] mm: zswap: Compress batching with Intel IAA
> in zswap_store() of large folios.
>
> On Wed, Feb 05, 2025 at 11:21:01PM -0800, Kanchana P Sridhar wrote:
> > zswap_compress_folio() is modified to detect if the pool's acomp_ctx has
> > more than one "nr_reqs", which will be the case if the cpu onlining code
> > has allocated multiple batching resources in the acomp_ctx. If so, it means
> > compress batching can be used with a batch-size of "acomp_ctx->nr_reqs".
> >
> > If compress batching can be used, zswap_compress_folio() will invoke the
> > newly added zswap_batch_compress() procedure to compress and store the
> > folio in batches of "acomp_ctx->nr_reqs" pages.
> >
> > With Intel IAA, the iaa_crypto driver will compress each batch of pages in
> > parallel in hardware.
> >
> > Hence, zswap_batch_compress() does the same computes for a batch, as
> > zswap_compress() does for a page; and returns true if the batch was
> > successfully compressed/stored, and false otherwise.
> >
> > If the pool does not support compress batching, or the folio has only one
> > page, zswap_compress_folio() calls zswap_compress() for each individual
> > page in the folio, as before.
> >
> > Signed-off-by: Kanchana P Sridhar <kanchana.p.sridhar@xxxxxxxxx>
> > ---
> > mm/zswap.c | 122
> +++++++++++++++++++++++++++++++++++++++++++++++++----
> > 1 file changed, 113 insertions(+), 9 deletions(-)
> >
> > diff --git a/mm/zswap.c b/mm/zswap.c
> > index 6563d12e907b..f1cba77eda62 100644
> > --- a/mm/zswap.c
> > +++ b/mm/zswap.c
> > @@ -985,10 +985,11 @@ static void acomp_ctx_put_unlock(struct
> crypto_acomp_ctx *acomp_ctx)
> > mutex_unlock(&acomp_ctx->mutex);
> > }
> >
> > +/* The per-cpu @acomp_ctx mutex should be locked/unlocked in the
> caller. */
>
> Please use lockdep assertions rather than comments for internal locking rules.
Sure. Thanks for the suggestion.
>
> > static bool zswap_compress(struct page *page, struct zswap_entry *entry,
> > - struct zswap_pool *pool)
> > + struct zswap_pool *pool,
> > + struct crypto_acomp_ctx *acomp_ctx)
> > {
> > - struct crypto_acomp_ctx *acomp_ctx;
> > struct scatterlist input, output;
> > int comp_ret = 0, alloc_ret = 0;
> > unsigned int dlen = PAGE_SIZE;
> > @@ -998,7 +999,6 @@ static bool zswap_compress(struct page *page,
> struct zswap_entry *entry,
> > gfp_t gfp;
> > u8 *dst;
> >
> > - acomp_ctx = acomp_ctx_get_cpu_lock(pool);
> > dst = acomp_ctx->buffers[0];
> > sg_init_table(&input, 1);
> > sg_set_page(&input, page, PAGE_SIZE, 0);
> > @@ -1051,7 +1051,6 @@ static bool zswap_compress(struct page *page,
> struct zswap_entry *entry,
> > else if (alloc_ret)
> > zswap_reject_alloc_fail++;
> >
> > - acomp_ctx_put_unlock(acomp_ctx);
> > return comp_ret == 0 && alloc_ret == 0;
> > }
> >
> > @@ -1509,20 +1508,125 @@ static void shrink_worker(struct work_struct
> *w)
> > * main API
> > **********************************/
> >
> > +/* The per-cpu @acomp_ctx mutex should be locked/unlocked in the
> caller. */
> > +static bool zswap_batch_compress(struct folio *folio,
> > + long index,
> > + unsigned int batch_size,
> > + struct zswap_entry *entries[],
> > + struct zswap_pool *pool,
> > + struct crypto_acomp_ctx *acomp_ctx)
> > +{
> > + int comp_errors[ZSWAP_MAX_BATCH_SIZE] = { 0 };
> > + unsigned int dlens[ZSWAP_MAX_BATCH_SIZE];
> > + struct page *pages[ZSWAP_MAX_BATCH_SIZE];
> > + unsigned int i, nr_batch_pages;
> > + bool ret = true;
> > +
> > + nr_batch_pages = min((unsigned int)(folio_nr_pages(folio) - index),
> batch_size);
> > +
> > + for (i = 0; i < nr_batch_pages; ++i) {
> > + pages[i] = folio_page(folio, index + i);
> > + dlens[i] = PAGE_SIZE;
> > + }
> > +
> > + /*
> > + * Batch compress @nr_batch_pages. If IAA is the compressor, the
> > + * hardware will compress @nr_batch_pages in parallel.
> > + */
>
> Please do not specifically mention IAA in zswap.c, as batching could be
> supported in the future by other compressors.
Ok.
>
> > + ret = crypto_acomp_batch_compress(
> > + acomp_ctx->reqs,
> > + NULL,
> > + pages,
> > + acomp_ctx->buffers,
> > + dlens,
> > + comp_errors,
> > + nr_batch_pages);
>
> Does crypto_acomp_batch_compress() not require calling
> crypto_wait_req()?
It actually doesn't. If the crypto_wait parameter is NULL, the API requires
the driver to provide a way to process request completions asynchronously,
as described in patch 2 that adds the crypto batching API.
>
> > +
> > + if (ret) {
> > + /*
> > + * All batch pages were successfully compressed.
> > + * Store the pages in zpool.
> > + */
> > + struct zpool *zpool = pool->zpool;
> > + gfp_t gfp = __GFP_NORETRY | __GFP_NOWARN |
> __GFP_KSWAPD_RECLAIM;
> > +
> > + if (zpool_malloc_support_movable(zpool))
> > + gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
> > +
> > + for (i = 0; i < nr_batch_pages; ++i) {
> > + unsigned long handle;
> > + char *buf;
> > + int err;
> > +
> > + err = zpool_malloc(zpool, dlens[i], gfp, &handle);
> > +
> > + if (err) {
> > + if (err == -ENOSPC)
> > + zswap_reject_compress_poor++;
> > + else
> > + zswap_reject_alloc_fail++;
> > +
> > + ret = false;
> > + break;
> > + }
> > +
> > + buf = zpool_map_handle(zpool, handle,
> ZPOOL_MM_WO);
> > + memcpy(buf, acomp_ctx->buffers[i], dlens[i]);
> > + zpool_unmap_handle(zpool, handle);
> > +
> > + entries[i]->handle = handle;
> > + entries[i]->length = dlens[i];
> > + }
> > + } else {
> > + /* Some batch pages had compression errors. */
> > + for (i = 0; i < nr_batch_pages; ++i) {
> > + if (comp_errors[i]) {
> > + if (comp_errors[i] == -ENOSPC)
> > + zswap_reject_compress_poor++;
> > + else
> > + zswap_reject_compress_fail++;
> > + }
> > + }
> > + }
>
> This function is awfully close to zswap_compress(). It's essentially a
> vectorized version and uses crypto_acomp_batch_compress() instead of
> crypto_acomp_compress().
>
> My questions are:
> - Can we use crypto_acomp_batch_compress() for the non-batched case as
> well to unify the code? Does it cause any regressions?
>
> - If we have to use different compressions APIs, can we at least reuse
> the rest of the code? We can abstract the compression call into a
> helper that chooses the appropriate API based on the batch size. The
> rest should be the same AFAICT.
All good ideas. Let me think about this some more, and gather some data.
Thanks,
Kanchana
>
> > +
> > + return ret;
> > +}
> > +
> > static bool zswap_compress_folio(struct folio *folio,
> > struct zswap_entry *entries[],
> > struct zswap_pool *pool)
> > {
> > long index, nr_pages = folio_nr_pages(folio);
> > + struct crypto_acomp_ctx *acomp_ctx;
> > + unsigned int batch_size;
> > + bool ret = true;
> >
> > - for (index = 0; index < nr_pages; ++index) {
> > - struct page *page = folio_page(folio, index);
> > + acomp_ctx = acomp_ctx_get_cpu_lock(pool);
> > + batch_size = acomp_ctx->nr_reqs;
> > +
> > + if ((batch_size > 1) && (nr_pages > 1)) {
> > + for (index = 0; index < nr_pages; index += batch_size) {
> > +
> > + if (!zswap_batch_compress(folio, index, batch_size,
> > + &entries[index], pool,
> acomp_ctx)) {
> > + ret = false;
> > + goto unlock_acomp_ctx;
> > + }
> > + }
> > + } else {
> > + for (index = 0; index < nr_pages; ++index) {
> > + struct page *page = folio_page(folio, index);
> >
> > - if (!zswap_compress(page, entries[index], pool))
> > - return false;
> > + if (!zswap_compress(page, entries[index], pool,
> acomp_ctx)) {
> > + ret = false;
> > + goto unlock_acomp_ctx;
> > + }
> > + }
> > }
> >
> > - return true;
> > +unlock_acomp_ctx:
> > + acomp_ctx_put_unlock(acomp_ctx);
> > + return ret;
> > }
> >
> > /*
> > --
> > 2.27.0
> >
