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From: Sergey Senozhatsky <senozhatsky@chromium.org>
To: Andrew Morton <akpm@linux-foundation.org>,
	Minchan Kim <minchan@kernel.org>
Cc: linux-kernel@vger.kernel.org,
	linux-block@vger.kernel.org,
	Sergey Senozhatsky <senozhatsky@chromium.org>
Subject: [PATCHv4 06/21] zram: pass estimated src size hint to zstd
Date: Wed, 15 May 2024 16:12:43 +0900
Message-ID: <20240515071645.1788128-7-senozhatsky@chromium.org>
In-Reply-To: <20240515071645.1788128-1-senozhatsky@chromium.org>
References: <20240515071645.1788128-1-senozhatsky@chromium.org>
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zram works with PAGE_SIZE buffers, so we always know exact
size of the source buffer and hence can pass estimated_src_size
to zstd_get_params().

This hint on x86_64, for example, reduces the size of the work
memory buffer from 1303520 bytes down to 90080 bytes. Given that
compression streams are per-CPU that's quite some memory saving.

Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
---
 drivers/block/zram/backend_zstd.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/block/zram/backend_zstd.c b/drivers/block/zram/backend_zstd.c
index bfe836844232..f930e9828be2 100644
--- a/drivers/block/zram/backend_zstd.c
+++ b/drivers/block/zram/backend_zstd.c
@@ -35,7 +35,7 @@ static void *zstd_create(void)
 		return NULL;
 
 	ctx->level = zstd_default_clevel();
-	params = zstd_get_params(ctx->level, 0);
+	params = zstd_get_params(ctx->level, PAGE_SIZE);
 	sz = zstd_cctx_workspace_bound(&params.cParams);
 	ctx->cctx_mem = vzalloc(sz);
 	if (!ctx->cctx_mem)
@@ -65,7 +65,7 @@ static int zstd_compress(void *ctx, const unsigned char *src,
 			 unsigned char *dst, size_t *dst_len)
 {
 	struct zstd_ctx *zctx = ctx;
-	const zstd_parameters params = zstd_get_params(zctx->level, 0);
+	const zstd_parameters params = zstd_get_params(zctx->level, PAGE_SIZE);
 	size_t ret;
 
 	ret = zstd_compress_cctx(zctx->cctx, dst, *dst_len,
-- 
2.45.0.rc1.225.g2a3ae87e7f-goog