From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-187.mta1.migadu.com (out-187.mta1.migadu.com [95.215.58.187]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3686E365A11 for ; Fri, 15 May 2026 00:53:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.187 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778806397; cv=none; b=dUCqhqazY7b9jFPJfar6JFCFTWN4LuXUX/1s2WgQo9pJPGc/3Qdw5FpHKy5RRUVGoSMe+3K5CIV410W3SCEJO71umd9giztCSQxa1HGvVQ6e0P2SscN8d+YiztcaYjjdFHzuCsvRc4fsJHAlS3AbUjCENWHXne/OCgEfac1zy1g= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778806397; c=relaxed/simple; bh=mzpNBAnnZtlTx7xoe9u25CdBveL0M7o9RwpTD4ywYx8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=qCgFN3Ykc/NWt2VAYzQ0KQfwnKC8P9DOc9Y/Utsih7VRjDXpSinKxN5j68GxoVGl9cFidpjKpw7xa6pofdT5tZe1f3+p++qvV5kK040KHH5RNcj6LItKpQJgguTCgA/utE0MoCmau4TwmUNj4pJsWG56QKEcIkMEQtCVEHqi6b0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=XiPfRUva; arc=none smtp.client-ip=95.215.58.187 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XiPfRUva" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1778806391; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=G6cvev44iqtouhYC9OJx9EHS+oUV8c83927GdbHHCjI=; b=XiPfRUvaxoNdZx2uY4Wax+VLJqdA8jaIHC2T6Lleii3Hc2zDzEM2X6yXK/mwrbMvZTmGVZ kcwu8m2T9FSA1gviU4x9jpW7FC6kD9iUXo9A1V4ihxraHa0DJHU2bL2JKoLfJ39A3VE1lb TgojvCN8uh2Hf0LwS6WavdNnLewJtj0= From: Ihor Solodrai To: Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Kumar Kartikeya Dwivedi Cc: Puranjay Mohan , Shakeel Butt , Mykyta Yatsenko , bpf@vger.kernel.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH bpf-next v5 3/3] bpf: Cache build IDs in sleepable stackmap path Date: Thu, 14 May 2026 17:52:44 -0700 Message-ID: <20260515005244.1333013-4-ihor.solodrai@linux.dev> In-Reply-To: <20260515005244.1333013-1-ihor.solodrai@linux.dev> References: <20260515005244.1333013-1-ihor.solodrai@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT Stack traces often contain adjacent IPs from the same VMA or from different VMAs backed by the same ELF file. Cache the last successfully parsed build ID together with the resolved VMA range and backing file so the sleepable build-ID path can avoid repeated VMA locking and file parsing in common cases. Suggested-by: Mykyta Yatsenko Acked-by: Mykyta Yatsenko Signed-off-by: Ihor Solodrai --- kernel/bpf/stackmap.c | 56 ++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 53 insertions(+), 3 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 08f7659505d1..7336fd55c856 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -230,13 +230,33 @@ static void stack_map_get_build_id_offset_sleepable(struct bpf_stack_build_id *i .vma = NULL, .mm = mm, }; - unsigned long vm_pgoff, vm_start; + struct { + struct file *file; + const unsigned char *build_id; + unsigned long vm_start; + unsigned long vm_end; + unsigned long vm_pgoff; + } cache = {}; + unsigned long vm_pgoff, vm_start, vm_end; struct vm_area_struct *vma; struct file *file; u64 ip; for (u32 i = 0; i < trace_nr; i++) { ip = READ_ONCE(id_offs[i].ip); + + /* + * Range cache fast path: if ip falls within the previously + * resolved VMA range, reuse the cache build_id without + * re-acquiring the VMA lock. + */ + if (cache.build_id && ip >= cache.vm_start && ip < cache.vm_end) { + vm_start = cache.vm_start; + vm_end = cache.vm_end; + vm_pgoff = cache.vm_pgoff; + goto build_id_valid; + } + vma = stack_map_lock_vma(&lock, ip); if (!vma || !vma->vm_file) { stack_map_build_id_set_ip(&id_offs[i]); @@ -244,9 +264,21 @@ static void stack_map_get_build_id_offset_sleepable(struct bpf_stack_build_id *i continue; } - file = get_file(vma->vm_file); + file = vma->vm_file; vm_pgoff = vma->vm_pgoff; vm_start = vma->vm_start; + vm_end = vma->vm_end; + + if (file == cache.file) { + /* + * Same backing file as previous (e.g. different VMAs + * of the same ELF binary). Reuse the cache build_id. + */ + stack_map_unlock_vma(&lock); + goto build_id_valid; + } + + file = get_file(file); stack_map_unlock_vma(&lock); /* build_id_parse_file() may block on filesystem reads */ @@ -255,11 +287,29 @@ static void stack_map_get_build_id_offset_sleepable(struct bpf_stack_build_id *i fput(file); continue; } - fput(file); + if (cache.file) + fput(cache.file); + cache.file = file; + cache.build_id = id_offs[i].build_id; + +build_id_valid: + /* + * In the slow path cache.build_id points to id_offs[i].build_id. + * Cache hits leave cache.build_id pointing at a prior slot, + * triggering the memcpy here. + */ + if (cache.build_id != id_offs[i].build_id) + memcpy(id_offs[i].build_id, cache.build_id, BUILD_ID_SIZE_MAX); + cache.vm_start = vm_start; + cache.vm_end = vm_end; + cache.vm_pgoff = vm_pgoff; id_offs[i].offset = (vm_pgoff << PAGE_SHIFT) + ip - vm_start; id_offs[i].status = BPF_STACK_BUILD_ID_VALID; } + + if (cache.file) + fput(cache.file); } /* -- 2.54.0