From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 09D9F2C08D2 for ; Sat, 14 Jun 2025 11:40:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=195.135.223.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749901240; cv=none; b=fP8g+fmhQDchd2T34ZNQQtoFYjiJbw4pdOdUP520xAsUHUff/WrzA8p77x3pPSI04y/NSJ4Wp81wEZBQfO6jXxYvcqCmfDr/ggUn5uR2+xIoGQfWDBD0vj1d58LjT1NswbcYx0trRIQ4sTu6RkI9GiyTJbNan4p5mcA281dHEgE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1749901240; c=relaxed/simple; bh=ZIYpkuU/T03fzdX/8jF6Kg6q4VaYgoZbs4ULm3W849w=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=LhYv/9UJwIUqKYbzatHs5ifY9X/x9NycUgV9dftbXYEMtE6IwO4iUz6cYPZ+YjPCmjv54y0sNFpAX7dLFVFej23zYdI/nYh/rqve+C9hkV614rwSg/WxsMmsXr5Uv4agl8DQP24/al+WH0XzFsymOuoZ5bbKTKpbERmHKeOwP78= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de; spf=pass smtp.mailfrom=suse.de; arc=none smtp.client-ip=195.135.223.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=suse.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=suse.de Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 64ED1219A0; Sat, 14 Jun 2025 11:40:37 +0000 (UTC) Authentication-Results: smtp-out1.suse.de; none Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 2A30C13A17; Sat, 14 Jun 2025 11:40:37 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id adOlCLVfTWj7UAAAD6G6ig (envelope-from ); Sat, 14 Jun 2025 11:40:37 +0000 Date: Sat, 14 Jun 2025 13:40:36 +0200 Message-ID: <87a56ar1or.wl-tiwai@suse.de> From: Takashi Iwai To: Christophe Leroy Cc: Jaroslav Kysela , Takashi Iwai , linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sound@vger.kernel.org, Herve Codina Subject: Re: [PATCH v3 0/4] ALSA: pcm: Convert SNDRV_PCM_IOCTL_SYNC_PTR to user_access_begin/user_access_end() In-Reply-To: References: User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: linux-sound@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Spamd-Result: default: False [-4.00 / 50.00]; REPLY(-4.00)[] X-Rspamd-Queue-Id: 64ED1219A0 X-Rspamd-Pre-Result: action=no action; module=replies; Message is reply to one we originated X-Rspamd-Action: no action X-Spam-Level: X-Spam-Flag: NO X-Rspamd-Server: rspamd1.dmz-prg2.suse.org X-Spam-Score: -4.00 On Sat, 14 Jun 2025 08:43:13 +0200, Christophe Leroy wrote: > > 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 v2: > - Fix macros to skip user_read_access_end() when user_read_access_begin() failed > - Fix some tabulations for properly aligning backslashes > > 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() Applied now all patches. Thanks! Takashi