From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from pegase1.c-s.fr (pegase1.c-s.fr [93.17.236.30]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AAF2320DD40; Fri, 13 Jun 2025 15:50:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=93.17.236.30 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749829847; cv=none; b=YPytSW7AcMdz2cZ93yHSkSC0Nk1tlNjrw42IZFvbPyWsO5wt0Q712FQRflNUunRhjTJMdEgeshfcSaFfdPyFqM6LEdKEH5JY3yRAX4S09xZCFxHxjJ8apxiqE5D9UX4rbiSRN6iSOvUpZ2twSgd0E/clzLb7mSFVQLu0uEE03aI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749829847; c=relaxed/simple; bh=jlE0SCVg7sa2yGK773TAr9cyOmP621uHgVHW+CuTNss=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Q4HEYWmpyqpuWoIyzzOClI+ImjOzMR7Zieiv2MBCG/zxHaDVJlzCoPLpHLTHmz0ECyIChuvaL/ujWfPk6SSTGrUaA75lQtZLebWOBoRWD49xCGgKH+ltTI4dwTS7EVaxXAFvE8/B7lg8Y9ABcBwtMT/Z1zuV/pRB3DWLjmuo/mQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu; spf=pass smtp.mailfrom=csgroup.eu; arc=none smtp.client-ip=93.17.236.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=csgroup.eu Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=csgroup.eu Received: from localhost (mailhub3.si.c-s.fr [192.168.12.233]) by localhost (Postfix) with ESMTP id 4bJk6P0b8rz9sqS; Fri, 13 Jun 2025 17:37:17 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from pegase1.c-s.fr ([192.168.12.234]) by localhost (pegase1.c-s.fr [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id PCOWwKqZyxEi; Fri, 13 Jun 2025 17:37:16 +0200 (CEST) Received: from messagerie.si.c-s.fr (messagerie.si.c-s.fr [192.168.25.192]) by pegase1.c-s.fr (Postfix) with ESMTP id 4bJk6N70qRz9sfW; Fri, 13 Jun 2025 17:37:16 +0200 (CEST) Received: from localhost (localhost [127.0.0.1]) by messagerie.si.c-s.fr (Postfix) with ESMTP id EA98D8B77C; Fri, 13 Jun 2025 17:37:16 +0200 (CEST) X-Virus-Scanned: amavisd-new at c-s.fr Received: from messagerie.si.c-s.fr ([127.0.0.1]) by localhost (messagerie.si.c-s.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id uYUCd0b22SLg; Fri, 13 Jun 2025 17:37:16 +0200 (CEST) Received: from PO20335.idsi0.si.c-s.fr (unknown [192.168.235.99]) by messagerie.si.c-s.fr (Postfix) with ESMTP id 7EAB98B769; Fri, 13 Jun 2025 17:37:16 +0200 (CEST) From: Christophe Leroy To: Jaroslav Kysela , Takashi Iwai Cc: Christophe Leroy , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sound@vger.kernel.org, Herve Codina Subject: [PATCH v2 0/4] ALSA: pcm: Convert SNDRV_PCM_IOCTL_SYNC_PTR to user_access_begin/user_access_end() Date: Fri, 13 Jun 2025 17:37:07 +0200 Message-ID: X-Mailer: git-send-email 2.47.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1749829028; l=4560; i=christophe.leroy@csgroup.eu; s=20211009; h=from:subject:message-id; bh=jlE0SCVg7sa2yGK773TAr9cyOmP621uHgVHW+CuTNss=; b=l3AE6pDZs6HimY4utPStAcfFbd+gbXdCu8zDpmIt5piqkMbaCvlsaxClGqOAATPsTE1XXP09k egnLVqIAslQBYOxh25axpEMO/3bqyyVB9LNIfigGUmGlGOz21+2HS/t X-Developer-Key: i=christophe.leroy@csgroup.eu; a=ed25519; pk=HIzTzUj91asvincQGOFx6+ZF5AoUuP9GdOtQChs7Mm0= Content-Transfer-Encoding: 8bit This series converts all variants of SNDRV_PCM_IOCTL_SYNC_PTR to user_access_begin/user_access_end() in order to reduce the CPU load measured in function snd_pcm_ioctl. With the current implementation, "perf top" reports a high load in snd_pcm_iotcl(). Most calls to that function are SNDRV_PCM_IOCTL_SYNC_PTR. 14.20% test_perf [.] engine_main ==> 12.86% [kernel] [k] snd_pcm_ioctl 11.91% [kernel] [k] finish_task_switch.isra.0 4.15% [kernel] [k] snd_pcm_group_unlock_irq.part.0 4.07% libc.so.6 [.] __ioctl_time64 3.58% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin_generic 3.37% [kernel] [k] sys_ioctl 2.96% libasound.so.2.0.0 [.] snd_pcm_hw_avail_update 2.73% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin 2.58% [kernel] [k] system_call_exception 1.93% libasound.so.2.0.0 [.] sync_ptr1 1.85% libasound.so.2.0.0 [.] snd_pcm_unlock 1.84% libasound.so.2.0.0 [.] snd_pcm_mmap_begin 1.83% libasound.so.2.0.0 [.] bad_pcm_state 1.68% libasound.so.2.0.0 [.] snd_pcm_mmap_avail 1.67% libasound.so.2.0.0 [.] snd_pcm_avail_update A tentative was done with going via intermediaire structs on stack to replace the multiple get_user() and put_user() with copy_from_user() and copy_to_user(). But copy_from_user() calls _copy_from_user() and copy_to_user() calls _copy_to_user(). Both then call __copy_tofrom_user(). In total it is 16.4% so it is worse than before. 14.47% test_perf [.] engine_main 12.00% [kernel] [k] finish_task_switch.isra.0 ==> 8.37% [kernel] [k] snd_pcm_ioctl 5.44% libc.so.6 [.] __ioctl_time64 5.03% [kernel] [k] snd_pcm_group_unlock_irq.part.0 ==> 4.86% [kernel] [k] __copy_tofrom_user 4.62% [kernel] [k] sys_ioctl 3.22% [kernel] [k] system_call_exception 2.42% libasound.so.2.0.0 [.] snd_pcm_mmap_begin 2.31% [kernel] [k] fdget 2.23% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin_generic 2.19% [kernel] [k] syscall_exit_prepare 1.92% libasound.so.2.0.0 [.] snd_pcm_mmap_avail 1.86% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin 1.68% libasound.so.2.0.0 [.] snd_pcm_hw_avail_update ==> 1.67% [kernel] [k] _copy_from_user 1.66% libasound.so.2.0.0 [.] bad_pcm_state ==> 1.53% [kernel] [k] _copy_to_user 1.40% libasound.so.2.0.0 [.] sync_ptr1 With this series which uses unsafe_put_user() and unsafe_get_user(), the load is significantly reduced: 17.46% test_perf [.] engine_main 9.14% [kernel] [k] finish_task_switch.isra.0 ==> 4.92% [kernel] [k] snd_pcm_ioctl 3.99% [kernel] [k] snd_pcm_group_unlock_irq.part.0 3.71% libc.so.6 [.] __ioctl_time64 3.61% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin_generic 2.72% libasound.so.2.0.0 [.] sync_ptr1 2.65% [kernel] [k] system_call_exception 2.46% [kernel] [k] sys_ioctl 2.43% [kernel] [k] __rseq_handle_notify_resume 2.34% [kernel] [k] do_epoll_wait 2.30% libasound.so.2.0.0 [.] __snd_pcm_mmap_commit 2.14% libasound.so.2.0.0 [.] __snd_pcm_avail 2.04% libasound.so.2.0.0 [.] snd_pcm_hw_avail_update 1.89% libasound.so.2.0.0 [.] snd_pcm_lock 1.84% libasound.so.2.0.0 [.] snd_pcm_mmap_avail 1.76% libasound.so.2.0.0 [.] __snd_pcm_avail_update 1.61% libasound.so.2.0.0 [.] bad_pcm_state 1.60% libasound.so.2.0.0 [.] __snd_pcm_mmap_begin 1.49% libasound.so.2.0.0 [.] query_status_data Since RFC: - Added a cover letter to summarize some of the measurements done on and around the RFC - Fixed relevant checkpatch feedback - Split last patch in two Christophe Leroy (4): ALSA: pcm: refactor copy from/to user in SNDRV_PCM_IOCTL_SYNC_PTR ALSA: pcm: Convert SNDRV_PCM_IOCTL_SYNC_PTR to user_access_begin/user_access_end() ALSA: pcm: Replace [audio_]tstamp_[n]sec by struct __snd_timespec in struct snd_pcm_mmap_status32 ALSA: pcm: Convert snd_pcm_sync_ptr() to user_access_begin/user_access_end() sound/core/pcm_compat.c | 14 +----- sound/core/pcm_native.c | 96 +++++++++++++++++++++++++---------------- 2 files changed, 62 insertions(+), 48 deletions(-) -- 2.47.0