The patch titled
Subject: zram: add dictionary support to zstd backend
has been added to the -mm mm-unstable branch. Its filename is
zram-add-dictionary-support-to-zstd-backend.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-add-dictionary-support-to-zstd-backend.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: add dictionary support to zstd backend
Date: Wed, 15 May 2024 16:12:52 +0900
This adds support for pre-trained zstd dictionaries [1] Dictionary is
loaded once (per-config) and then loaded to Cctx and Dctx by reference, so
we don't allocate extra memory.
Regarding GFP_ATOMIC in Cctx customAlloc(), we probably would want to do
something about it. Either make sure that we always (somehow) fully setup
all Cctx contexts from non-atomic context before we attempt to use them,
come up with some sort of custom allocator or stop calling
zcomp_compress() from atomic context.
TEST
====
- default zstd
/sys/block/zram0/mm_stat
1750315008 504602831 514256896 0 514256896 1 0 34204 34204
- zstd level=7 dict=/etc/dictionary
/sys/block/zram0/mm_stat
1750310912 432540606 441712640 0 441712640 1 0 34187 34187
[1] https://github.com/facebook/zstd/blob/dev/programs/zstd.1.md#dictionary-builder
Link: https://lkml.kernel.org/r/20240515071645.1788128-16-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Nick Terrell <terrelln@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/zram/backend_zstd.c | 126 ++++++++++++++++++++++------
1 file changed, 101 insertions(+), 25 deletions(-)
--- a/drivers/block/zram/backend_zstd.c~zram-add-dictionary-support-to-zstd-backend
+++ a/drivers/block/zram/backend_zstd.c
@@ -12,23 +12,52 @@ struct zstd_ctx {
zstd_dctx *dctx;
void *cctx_mem;
void *dctx_mem;
+ zstd_custom_mem ctx_mem;
+ zstd_cdict *cdict;
+ zstd_ddict *ddict;
s32 level;
};
+/*
+ * Cctx allocator.customAlloc() can be called from zcomp_compress() under
+ * local-lock (per-CPU compression stream), in which case we must use
+ * GFP_ATOMIC.
+ */
+static void *zstd_ctx_alloc(void *opaque, size_t size)
+{
+ if (!preemptible())
+ return kvzalloc(size, GFP_ATOMIC);
+
+ return kvzalloc(size, GFP_KERNEL);
+}
+
+static void zstd_ctx_free(void *opaque, void *address)
+{
+ kvfree(address);
+}
+
static void zstd_destroy(void *ctx)
{
struct zstd_ctx *zctx = ctx;
- vfree(zctx->cctx_mem);
- vfree(zctx->dctx_mem);
+ if (zctx->cctx_mem)
+ vfree(zctx->cctx_mem);
+ else
+ zstd_free_cctx(zctx->cctx);
+
+ if (zctx->dctx_mem)
+ vfree(zctx->dctx_mem);
+ else
+ zstd_free_dctx(zctx->dctx);
+
+ zstd_free_cdict(zctx->cdict);
+ zstd_free_ddict(zctx->ddict);
kfree(zctx);
}
static void *zstd_create(struct zcomp_config *config)
{
- zstd_parameters params;
struct zstd_ctx *ctx;
- size_t sz;
ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
if (!ctx)
@@ -39,24 +68,62 @@ static void *zstd_create(struct zcomp_co
else
ctx->level = zstd_default_clevel();
- params = zstd_get_params(ctx->level, PAGE_SIZE);
- sz = zstd_cctx_workspace_bound(¶ms.cParams);
- ctx->cctx_mem = vzalloc(sz);
- if (!ctx->cctx_mem)
- goto error;
-
- ctx->cctx = zstd_init_cctx(ctx->cctx_mem, sz);
- if (!ctx->cctx)
- goto error;
-
- sz = zstd_dctx_workspace_bound();
- ctx->dctx_mem = vzalloc(sz);
- if (!ctx->dctx_mem)
- goto error;
-
- ctx->dctx = zstd_init_dctx(ctx->dctx_mem, sz);
- if (!ctx->dctx)
- goto error;
+ ctx->ctx_mem.customAlloc = zstd_ctx_alloc;
+ ctx->ctx_mem.customFree = zstd_ctx_free;
+
+ if (config->dict_sz == 0) {
+ zstd_parameters params;
+ size_t sz;
+
+ params = zstd_get_params(ctx->level, PAGE_SIZE);
+ sz = zstd_cctx_workspace_bound(¶ms.cParams);
+ ctx->cctx_mem = vzalloc(sz);
+ if (!ctx->cctx_mem)
+ goto error;
+
+ ctx->cctx = zstd_init_cctx(ctx->cctx_mem, sz);
+ if (!ctx->cctx)
+ goto error;
+
+ sz = zstd_dctx_workspace_bound();
+ ctx->dctx_mem = vzalloc(sz);
+ if (!ctx->dctx_mem)
+ goto error;
+
+ ctx->dctx = zstd_init_dctx(ctx->dctx_mem, sz);
+ if (!ctx->dctx)
+ goto error;
+ } else {
+ zstd_compression_parameters params;
+
+ ctx->cctx = zstd_create_cctx_advanced(ctx->ctx_mem);
+ if (!ctx->cctx)
+ goto error;
+
+ ctx->dctx = zstd_create_dctx_advanced(ctx->ctx_mem);
+ if (!ctx->dctx)
+ goto error;
+
+ params = zstd_get_cparams(ctx->level, PAGE_SIZE,
+ config->dict_sz);
+
+ ctx->cdict = zstd_create_cdict_advanced(config->dict,
+ config->dict_sz,
+ ZSTD_dlm_byRef,
+ ZSTD_dct_auto,
+ params,
+ ctx->ctx_mem);
+ if (!ctx->cdict)
+ goto error;
+
+ ctx->ddict = zstd_create_ddict_advanced(config->dict,
+ config->dict_sz,
+ ZSTD_dlm_byRef,
+ ZSTD_dct_auto,
+ ctx->ctx_mem);
+ if (!ctx->ddict)
+ goto error;
+ }
return ctx;
@@ -72,8 +139,12 @@ static int zstd_compress(void *ctx, cons
const zstd_parameters params = zstd_get_params(zctx->level, PAGE_SIZE);
size_t ret;
- ret = zstd_compress_cctx(zctx->cctx, dst, *dst_len,
- src, PAGE_SIZE, ¶ms);
+ if (!zctx->cdict)
+ ret = zstd_compress_cctx(zctx->cctx, dst, *dst_len,
+ src, PAGE_SIZE, ¶ms);
+ else
+ ret = zstd_compress_using_cdict(zctx->cctx, dst, *dst_len,
+ src, PAGE_SIZE, zctx->cdict);
if (zstd_is_error(ret))
return -EINVAL;
*dst_len = ret;
@@ -86,7 +157,12 @@ static int zstd_decompress(void *ctx, co
struct zstd_ctx *zctx = ctx;
size_t ret;
- ret = zstd_decompress_dctx(zctx->dctx, dst, PAGE_SIZE, src, src_len);
+ if (!zctx->ddict)
+ ret = zstd_decompress_dctx(zctx->dctx, dst, PAGE_SIZE,
+ src, src_len);
+ else
+ ret = zstd_decompress_using_ddict(zctx->dctx, dst, PAGE_SIZE,
+ src, src_len, zctx->ddict);
if (zstd_is_error(ret))
return -EINVAL;
return 0;
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-move-from-crypto-api-to-custom-comp-backends-api.patch
zram-add-lzo-and-lzorle-compression-backends-support.patch
zram-add-lz4-compression-backend-support.patch
zram-add-lz4hc-compression-backend-support.patch
zram-add-zstd-compression-backend-support.patch
zram-pass-estimated-src-size-hint-to-zstd.patch
zram-add-zlib-compression-backend-support.patch
zram-add-842-compression-backend-support.patch
zram-check-that-backends-array-has-at-least-one-backend.patch
zram-introduce-zcomp_config-structure.patch
zram-extend-comp_algorithm-attr-write-handling.patch
zram-support-compression-level-comp-config.patch
zram-add-support-for-dict-comp-config.patch
lib-zstd-export-api-needed-for-dictionary-support.patch
zram-add-dictionary-support-to-zstd-backend.patch
zram-add-config-init-release-backend-callbacks.patch
zram-share-dictionaries-between-per-cpu-contexts.patch
zram-add-dictionary-support-to-lz4.patch
lib-lz4hc-export-lz4_resetstreamhc-symbol.patch
zram-add-dictionary-support-to-lz4hc.patch
documentation-zram-add-documentation-for-algorithm-parameters.patch
