From: Johannes Weiner <hannes@cmpxchg.org>
To: Usama Arif <usama.arif@linux.dev>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
davem@davemloft.net, terrelln@fb.com, dsterba@suse.com,
yosry@kernel.org, nphamcs@gmail.com, chengming.zhou@linux.dev,
Andrew Morton <akpm@linux-foundation.org>,
linux-crypto@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, riel@surriel.com,
shakeel.butt@linux.dev, kernel-team@meta.com
Subject: Re: [PATCH 2/2] crypto: deflate - use vmalloc() for stream workspaces
Date: Thu, 12 Nov 2026 11:26:46 -0500 [thread overview]
Message-ID: <avXoxnMq6ns8AK0z@cmpxchg.org> (raw)
In-Reply-To: <20261111153532.1036709-3-usama.arif@linux.dev>
On Wed, Nov 11, 2026 at 07:07:40AM -0800, Usama Arif wrote:
> The deflate acomp streams outlive the transforms that use them. One
> stream is allocated during transform initialization; additional
> per-CPU streams are allocated on demand. They are freed only when
> the algorithm is unregistered.
>
> In a 4 KiB-page x86-64 build, each stream requests 145,320 bytes.
> If kvmalloc() succeeds via kmalloc(), it occupies an order-6 block
> (256 KiB). vmalloc() needs 36 backing pages (144 KiB), 112 KiB fewer
> per stream. Across 384 populated streams, that is 42 MiB less
> workspace backing if all would have used kmalloc(). There is no such
> gain when kvmalloc() already falls back to vmalloc().
>
> Use vmalloc() and vfree() directly, as the crypto lz4 implementations
> already do. This uses vmalloc address space, page tables and
> bookkeeping; the figures above compare workspace backing only.
>
> Signed-off-by: Usama Arif <usama.arif@linux.dev>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
prev parent reply other threads:[~2026-11-12 16:26 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-11 15:07 [PATCH 0/2] crypto: use vmalloc() for large stream workspaces Usama Arif
2026-11-11 15:07 ` [PATCH 1/2] crypto: zstd - use vmalloc() for " Usama Arif
2026-11-11 15:43 ` Rik van Riel
2026-11-12 16:21 ` Johannes Weiner
2026-11-11 15:07 ` [PATCH 2/2] crypto: deflate " Usama Arif
2026-11-11 15:44 ` Rik van Riel
2026-11-12 16:26 ` Johannes Weiner [this message]
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