From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 5A509C77B7D for ; Mon, 15 May 2023 16:44:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date:Subject:Cc :To:From:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References: List-Owner; bh=2GWoZ71s/Pfwt4E5Ns0AsDfc0Sap94Nb/7aMWs+Ehis=; b=gM9yttiHmhpyif OhTf2+dgwbfUYBQjp5iRxX7ZPU23imDypAipnPPBl7Cp1NUPWsl9ZOxMW48Ta8uTd2ab7Js9NwGog pLGYeJn3mjTH7zXacyITXzoqxMa+mTlk21wepOdRQ8zvtOPxdaAPtif1qMYMy1rYB0PgzQ1XjjdjL gSCCdwADTEYdPVPzAacG3I1eqKteeZLIYAhPxfcv1aiHjbvx0BcCnep9AD0EX7MI1TU/0q1/deZtW OrWOAj+jC7mmLmRHdxqsQtNtYVyy4VrEEgxw1exdeTBh09QfSdwdes0FHF1QJz5AKsLTTV27K23/e k34lO6GgqFQis8R0kBPg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1pybIb-002o8C-1i; Mon, 15 May 2023 16:43:49 +0000 Received: from galois.linutronix.de ([193.142.43.55]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1pybIZ-002o6C-0U for linux-arm-kernel@lists.infradead.org; Mon, 15 May 2023 16:43:48 +0000 From: Thomas Gleixner DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1684169021; 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; bh=hFJvl7LIktbBCQ1SyA1NJ2Cms/GCM39PTTVcTkrL/sU=; b=y63P0Tvr5peIGLAfqQ3o8V4fFS8LbGVupCFXakDXRKbt1HOBb4qSeDkmIYiYC8NrcNcQxH SBCCRHY/k/PhVfOPzUok7NkRLWIAZ3HnQt3SPhv0DVxFgqnlsSgf9p9e7gvauHFpikRxpJ jNRLuKPlYWwOUtSm7P/m8wxyDNHbNrPCiTyN1zgSRBp0ZgaGPlA9gXIcUw1SUGTEmvK2tk IqSf12G60ylzlcX8YWqRa4z3BC3pRAG28fen1nbPiRkTQMe5LbPxPfzL9tDw4/NVNLDSJ3 SxKf6L2oU6/OlSOPnh3kunY6DGR1jamkBM+z40DYgsbqSNoFWT/9GlUsfBgACQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684169021; 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; bh=hFJvl7LIktbBCQ1SyA1NJ2Cms/GCM39PTTVcTkrL/sU=; b=Ja5EEyFSWzhxflA9/YmV4Dt0KlDUvunOlw9bTerG1NcVQhAllHubMnc6a4dSIn4qyCFUa2 Ya/gi+Jyj0M2AaBw== To: Andrew Morton Cc: linux-mm@kvack.org, Christoph Hellwig , Uladzislau Rezki , Lorenzo Stoakes , Peter Zijlstra , Baoquan He , John Ogness , linux-arm-kernel@lists.infradead.org, Russell King , Mark Rutland , Marc Zyngier Subject: Excessive TLB flush ranges Date: Mon, 15 May 2023 18:43:40 +0200 Message-ID: <87a5y5a6kj.ffs@tglx> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230515_094347_347998_3305B607 X-CRM114-Status: UNSURE ( 9.21 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Folks! We're observing massive latencies and slowdowns on ARM32 machines due to excessive TLB flush ranges. Those can be observed when tearing down a process, which has a seccomp BPF filter installed. ARM32 uses the vmalloc area for module space. bpf_prog_free_deferred() vfree() _vm_unmap_aliases() collect_per_cpu_vmap_blocks: start:0x95c8d000 end:0x95c8e000 size:0x1000 __purge_vmap_area_lazy(start:0x95c8d000, end:0x95c8e000) va_start:0xf08a1000 va_end:0xf08a5000 size:0x00004000 gap:0x5ac13000 (371731 pages) va_start:0xf08a5000 va_end:0xf08a9000 size:0x00004000 gap:0x00000000 ( 0 pages) va_start:0xf08a9000 va_end:0xf08ad000 size:0x00004000 gap:0x00000000 ( 0 pages) va_start:0xf08ad000 va_end:0xf08b1000 size:0x00004000 gap:0x00000000 ( 0 pages) va_start:0xf08b3000 va_end:0xf08b7000 size:0x00004000 gap:0x00002000 ( 2 pages) va_start:0xf08b7000 va_end:0xf08bb000 size:0x00004000 gap:0x00000000 ( 0 pages) va_start:0xf08bb000 va_end:0xf08bf000 size:0x00004000 gap:0x00000000 ( 0 pages) va_start:0xf0a15000 va_end:0xf0a17000 size:0x00002000 gap:0x00156000 ( 342 pages) flush_tlb_kernel_range(start:0x95c8d000, end:0xf0a17000) Does 372106 flush operations where only 31 are useful So for all architectures which lack a mechanism to do a full TLB flush in flush_tlb_kernel_range() this takes ages (4-8ms) and slows down realtime processes on the other CPUs by a factor of two and larger. So while ARM32, CSKY, NIOS, PPC (some variants), _should_ arguably have a fallback to tlb_flush_all() when the range is too large, there is another issue. I've seen a couple of instances where _vm_unmap_aliases() collects one page and the actual va list has only 2 pages, which might be eventually worth to flush one by one. I'm not sure whether that's worth it as checking for those gaps might be too expensive for the case where a large number of va entries needs to be flushed. We'll experiment with a tlb_flush_all() fallback on that ARM32 system in the next days and see how that works out. Thanks, tglx _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel