From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta1.migadu.com (out-171.mta1.migadu.com [95.215.58.171]) (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 B478434C99C for ; Wed, 22 Oct 2025 15:15:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761146115; cv=none; b=oxbZiAiVhEoUbdrXu8C8FBDqMywenUalRIO1oIbrHK/8uix8n0hkF6wjQBFI9vBvAoBBdoB+VoCyK5n+OHzoUv3T3LTcjiDUbpgrnrYWW3pEcPkP20nu7ELRP29kNyLxfMEL2CWzE1W0b63GtfwufwKw4Nt73TO7/PUQY3ODZqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761146115; c=relaxed/simple; bh=4mblRB768g0mR+5jJ6ggp8VkkejsrNbpM/I/hxaLvgQ=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=K4SGSC56wLzOMOo8bPkjJB0vZNzxP/HJVmUfxvs7USh0GG/fTxouh3gM17KvGzHJeyEOhjWw5AA5FxyIqzN6ffiEv5Z2s6+bE1KKB8KeIxXz0cmOA+JAriI8FEHIsCog+RGhgUQtkwBacLX8Bhcb3FXuQJuRNVds377k0Rj/nWM= 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=gDv9PvMw; arc=none smtp.client-ip=95.215.58.171 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="gDv9PvMw" Message-ID: <947b1121-ddfc-4f49-825d-103699b62d0c@linux.dev> DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1761146101; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=gPD7KYgHjZ2Kx2EBhuhfRI/lFZmifGXs9ZgWPA9xXqg=; b=gDv9PvMwi7yFV5RizFwxLazuRUHH3JAn2AKGNIfPpXeMPmJmGEaUAgN4Ns2irU/AQMwql+ AcxaIN3Jh4BpVJWspOqCcRpLJjth8UmNYw1q1uN+iFQoCvEshG5BYuyFS7xMdtaieY32/Y Wr3OEOsJJ8w4GhFNCE7pHbAqFab3CwE= Date: Wed, 22 Oct 2025 23:14:46 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH bpf-next v3 1/2] perf: Use extern perf_callchain_entry for get_perf_callchain To: Peter Zijlstra Cc: mingo@redhat.com, acme@kernel.org, namhyung@kernel.org, mark.rutland@arm.com, alexander.shishkin@linux.intel.com, jolsa@kernel.org, irogers@google.com, adrian.hunter@intel.com, kan.liang@linux.intel.com, song@kernel.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org References: <20251019170118.2955346-1-chen.dylane@linux.dev> <20251019170118.2955346-2-chen.dylane@linux.dev> <20251020114040.GT3419281@noisy.programming.kicks-ass.net> X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Tao Chen In-Reply-To: <20251020114040.GT3419281@noisy.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 在 2025/10/20 19:40, Peter Zijlstra 写道: Hi, Peter > On Mon, Oct 20, 2025 at 01:01:17AM +0800, Tao Chen wrote: >> From bpf stack map, we want to use our own buffers to avoid unnecessary >> copy, so let us pass it directly. BPF will use this in the next patch. >> >> Signed-off-by: Tao Chen >> --- > >> diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c >> index 808c0d7a31f..851e8f9d026 100644 >> --- a/kernel/events/callchain.c >> +++ b/kernel/events/callchain.c >> @@ -217,8 +217,8 @@ static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entr >> } >> >> struct perf_callchain_entry * >> -get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, >> - u32 max_stack, bool crosstask, bool add_mark) >> +get_perf_callchain(struct pt_regs *regs, struct perf_callchain_entry *external_entry, >> + bool kernel, bool user, u32 max_stack, bool crosstask, bool add_mark) >> { >> struct perf_callchain_entry *entry; >> struct perf_callchain_entry_ctx ctx; >> @@ -228,7 +228,11 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, >> if (crosstask && user && !kernel) >> return NULL; >> >> - entry = get_callchain_entry(&rctx); >> + if (external_entry) >> + entry = external_entry; >> + else >> + entry = get_callchain_entry(&rctx); >> + >> if (!entry) >> return NULL; >> >> @@ -260,7 +264,8 @@ get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, >> } >> >> exit_put: >> - put_callchain_entry(rctx); >> + if (!external_entry) >> + put_callchain_entry(rctx); >> >> return entry; >> } > > Urgh.. How about something like the below, and then you fix up > __bpf_get_stack() a little like this: > Your solution seems to be more scalable, i will develop based on yours，thanks a lot. > > diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c > index 4d53cdd1374c..8b85b49cecf7 100644 > --- a/kernel/bpf/stackmap.c > +++ b/kernel/bpf/stackmap.c > @@ -303,8 +303,8 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, > u32 max_depth = map->value_size / stack_map_data_size(map); > u32 skip = flags & BPF_F_SKIP_FIELD_MASK; > bool user = flags & BPF_F_USER_STACK; > + struct perf_callchain_entry_ctx ctx; > struct perf_callchain_entry *trace; > - bool kernel = !user; > > if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | > BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) > @@ -314,8 +314,13 @@ BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, > if (max_depth > sysctl_perf_event_max_stack) > max_depth = sysctl_perf_event_max_stack; > > - trace = get_perf_callchain(regs, kernel, user, max_depth, > - false, false); > + trace = your-stuff; > + > + __init_perf_callchain_ctx(&ctx, trace, max_depth, false); > + if (!user) > + __get_perf_callchain_kernel(&ctx, regs); > + else > + __get_perf_callchain_user(&ctx, regs); > > if (unlikely(!trace)) > /* couldn't fetch the stack trace */ > > > > --- > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index fd1d91017b99..14a382cad1dd 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -67,6 +67,7 @@ struct perf_callchain_entry_ctx { > u32 nr; > short contexts; > bool contexts_maxed; > + bool add_mark; > }; > > typedef unsigned long (*perf_copy_f)(void *dst, const void *src, > @@ -1718,9 +1719,17 @@ DECLARE_PER_CPU(struct perf_callchain_entry, perf_callchain_entry); > > extern void perf_callchain_user(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs); > extern void perf_callchain_kernel(struct perf_callchain_entry_ctx *entry, struct pt_regs *regs); > + > +extern void __init_perf_callchain_ctx(struct perf_callchain_entry_ctx *ctx, > + struct perf_callchain_entry *entry, > + u32 max_stack, bool add_mark); > + > +extern void __get_perf_callchain_kernel(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs); > +extern void __get_perf_callchain_user(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs); > + > extern struct perf_callchain_entry * > get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, > - u32 max_stack, bool crosstask, bool add_mark); > + u32 max_stack, bool crosstask); > extern int get_callchain_buffers(int max_stack); > extern void put_callchain_buffers(void); > extern struct perf_callchain_entry *get_callchain_entry(int *rctx); > diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c > index 808c0d7a31fa..edd76e3bb139 100644 > --- a/kernel/events/callchain.c > +++ b/kernel/events/callchain.c > @@ -216,50 +216,70 @@ static void fixup_uretprobe_trampoline_entries(struct perf_callchain_entry *entr > #endif > } > > +void __init_perf_callchain_ctx(struct perf_callchain_entry_ctx *ctx, > + struct perf_callchain_entry *entry, > + u32 max_stack, bool add_mark) > + > +{ > + ctx->entry = entry; > + ctx->max_stack = max_stack; > + ctx->nr = entry->nr = 0; > + ctx->contexts = 0; > + ctx->contexts_maxed = false; > + ctx->add_mark = add_mark; > +} > + > +void __get_perf_callchain_kernel(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs) > +{ > + if (user_mode(regs)) > + return; > + > + if (ctx->add_mark) > + perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); > + perf_callchain_kernel(ctx, regs); > +} > + > +void __get_perf_callchain_user(struct perf_callchain_entry_ctx *ctx, struct pt_regs *regs) > +{ > + int start_entry_idx; > + > + if (!user_mode(regs)) { > + if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) > + return; > + regs = task_pt_regs(current); > + } > + > + if (ctx->add_mark) > + perf_callchain_store_context(ctx, PERF_CONTEXT_USER); > + > + start_entry_idx = entry->nr; > + perf_callchain_user(ctx, regs); > + fixup_uretprobe_trampoline_entries(entry, start_entry_idx); > +} > + > struct perf_callchain_entry * > get_perf_callchain(struct pt_regs *regs, bool kernel, bool user, > - u32 max_stack, bool crosstask, bool add_mark) > + u32 max_stack, bool crosstask) > { > - struct perf_callchain_entry *entry; > struct perf_callchain_entry_ctx ctx; > - int rctx, start_entry_idx; > + struct perf_callchain_entry *entry; > + int rctx; > > /* crosstask is not supported for user stacks */ > if (crosstask && user && !kernel) > return NULL; > > - entry = get_callchain_entry(&rctx); > + entry = get_callchain_entry(&rctx, regs); > if (!entry) > return NULL; > > - ctx.entry = entry; > - ctx.max_stack = max_stack; > - ctx.nr = entry->nr = 0; > - ctx.contexts = 0; > - ctx.contexts_maxed = false; > + __init_perf_callchain_ctx(&ctx, entry, max_stack, true); > > - if (kernel && !user_mode(regs)) { > - if (add_mark) > - perf_callchain_store_context(&ctx, PERF_CONTEXT_KERNEL); > - perf_callchain_kernel(&ctx, regs); > - } > + if (kernel) > + __get_perf_callchain_kernel(&ctx, regs); > + if (user && !crosstask) > + __get_perf_callchain_user(&ctx, regs); > > - if (user && !crosstask) { > - if (!user_mode(regs)) { > - if (current->flags & (PF_KTHREAD | PF_USER_WORKER)) > - goto exit_put; > - regs = task_pt_regs(current); > - } > - > - if (add_mark) > - perf_callchain_store_context(&ctx, PERF_CONTEXT_USER); > - > - start_entry_idx = entry->nr; > - perf_callchain_user(&ctx, regs); > - fixup_uretprobe_trampoline_entries(entry, start_entry_idx); > - } > - > -exit_put: > put_callchain_entry(rctx); > > return entry; > diff --git a/kernel/events/core.c b/kernel/events/core.c > index 177e57c1a362..cbe073d761a8 100644 > --- a/kernel/events/core.c > +++ b/kernel/events/core.c > @@ -8218,7 +8218,7 @@ perf_callchain(struct perf_event *event, struct pt_regs *regs) > return &__empty_callchain; > > callchain = get_perf_callchain(regs, kernel, user, > - max_stack, crosstask, true); > + max_stack, crosstask); > return callchain ?: &__empty_callchain; > } > -- Best Regards Tao Chen