From: "Alexei Starovoitov" <alexei.starovoitov@gmail.com>
To: "Emil Tsalapatis" <emil@etsalapatis.com>, <bpf@vger.kernel.org>
Cc: <andrii@kernel.org>, <eddyz87@gmail.com>, <memxor@gmail.com>,
<daniel@iogearbox.net>
Subject: Re: [PATCH bpf-next v3 5/7] selftests/bpf: libarena: Refill local caches in batches
Date: Tue, 27 Oct 2026 19:50:59 +0000 [thread overview]
Message-ID: <DMFVROPTON36.3LX4QMXFDA91K@gmail.com> (raw)
In-Reply-To: <20261023002056.6647-6-emil@etsalapatis.com>
On Thu, Oct 22, 2026 at 05:20 PM Emil Tsalapatis <emil@etsalapatis.com> wrote:
> + if (buddy_alloc_bulk(buddy, size, BUDDY_CACHE_BATCH_ORDER,
> + (void __arena * __arena *)slots->objects))
> + return NULL;
This asks for one block of order + 3. When the existing chunks have free
objects of this order, but no such block, it goes to buddy_chunk_get().
Before this patch the existing chunks served such buddy_alloc().
A sleepable prog takes another 1 MiB chunk.
A non-sleepable prog loses 1 MiB of buddy->vaddr in every buddy_alloc():
buddy_alloc() the cache is empty
buddy_cache_refill()
buddy_alloc_bulk() no free block of order + 3
buddy_chunk_get()
buddy_alloc_arena_vaddr() buddy->vaddr += 1 MiB
bpf_arena_free_pages() deferred to a worker
bpf_arena_alloc_pages() the range is still reserved: NULL
buddy_alloc_memory() one object from the existing chunks
the cache is still empty
After 1024 of them buddy_alloc_arena_vaddr() fails for sleepable progs
too.
Should the refill look at the existing chunks only,
like buddy_alloc_nogrow() in your other series?
next prev parent reply other threads:[~2026-10-27 19:51 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-23 0:20 [PATCH bpf-next v3 0/7] bpf libarena allocator improvements Emil Tsalapatis
2026-10-23 0:20 ` [PATCH bpf-next v3 1/7] selftests/bpf: libarena: Add bulk buddy allocation helpers Emil Tsalapatis
2026-10-23 0:49 ` bot+bpf-ci
2026-10-23 0:20 ` [PATCH bpf-next v3 2/7] selftests/bpf: Add a parallel buddy allocator benchmark Emil Tsalapatis
2026-10-23 0:20 ` [PATCH bpf-next v3 3/7] selftests/bpf: libarena: Add buddy per-CPU caches Emil Tsalapatis
2026-10-23 0:49 ` bot+bpf-ci
2026-10-23 0:20 ` [PATCH bpf-next v3 4/7] selftests/bpf: libarena: Handle NMI reentrancy Emil Tsalapatis
2026-10-27 19:49 ` Alexei Starovoitov
2026-10-27 21:03 ` Emil Tsalapatis
2026-10-23 0:20 ` [PATCH bpf-next v3 5/7] selftests/bpf: libarena: Refill local caches in batches Emil Tsalapatis
2026-10-27 19:50 ` Alexei Starovoitov [this message]
2026-10-27 20:57 ` Emil Tsalapatis
2026-10-28 4:51 ` Alexei Starovoitov
2026-10-23 0:20 ` [PATCH bpf-next v3 6/7] selftests/bpf: libarena: Add a transfer cache Emil Tsalapatis
2026-10-27 19:52 ` Alexei Starovoitov
2026-10-27 20:51 ` Emil Tsalapatis
2026-10-23 0:20 ` [PATCH bpf-next v3 7/7] selftests/bpf: libarena: Cover buddy cache fast paths Emil Tsalapatis
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