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bh=KmQgg157U5ZiEWaWvOuJFjaGuzOX9D+fHsfowoTsDj8=; b=QPI34lfuLTM7cfLvolcJESp5sZKtf336N2yUfdWQlYC1tQnBjG72a4efdkKS0Ebz0vI34G HGvedWOoWK0dOuDI+k9DZkY+pIZ9HU31WA8tLd8bc2ISVhs7A/0D/+VAdpaetge22Uff7K n9XRjBMH41/s63ntdFuxtkz7b7azoOvX0yud+Mwm0OJZFKfk/70IKLGfP6Mv5FK3YADeZZ LrbA22Y4V1Z6roS5IVAmF7UVOBX4kQS7Vdk4rRLd5iQuhxuhwaTla8hZ27OghHiHhXO5w5 GLriB4vELCWXigx03JLL9wVGTaLeF56FKFX4IuZo/hhqNowB8hzomZjAdpNEHg== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1684219039; 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: in-reply-to:in-reply-to:references:references; bh=KmQgg157U5ZiEWaWvOuJFjaGuzOX9D+fHsfowoTsDj8=; b=vHeBuibDTwpl4wMXML5ug2b9+24JDTzT4+wLQO47dw3BdoiZEhpE3oiYwzWDuATmq3ShL5 mD5Ld+ji0kJHlwDA== To: "Russell King (Oracle)" Cc: Andrew Morton , linux-mm@kvack.org, Christoph Hellwig , Uladzislau Rezki , Lorenzo Stoakes , Peter Zijlstra , Baoquan He , John Ogness , linux-arm-kernel@lists.infradead.org, Mark Rutland , Marc Zyngier , x86@kernel.org Subject: Re: Excessive TLB flush ranges In-Reply-To: References: <87a5y5a6kj.ffs@tglx> <87353x9y3l.ffs@tglx> <87zg658fla.ffs@tglx> Date: Tue, 16 May 2023 08:37:18 +0200 Message-ID: <87r0rg93z5.ffs@tglx> MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: o954uqa9eghkck8hkm7uje9eqse671e3 X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 3AE17140016 X-Rspam-User: X-HE-Tag: 1684219041-436922 X-HE-Meta: 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 hGXyQKuO UKXcGp5FjLhXLXKS/QrQ1emj7a6v+IwXE6qsVObWAgO9wWGM= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, May 15 2023 at 22:31, Russell King wrote: > On Mon, May 15, 2023 at 11:11:45PM +0200, Thomas Gleixner wrote: >> But that's not necessarily true for ARM32 as there are no IPIs involved >> on the machine we are using, which is a dual-core Cortex-A9. >> >> So I came up with the hack below, which is equally fast as the full >> flush variant while the performance impact on the other CPUs is minimally >> lower according to perf. >> >> That probably should have another argument which tells how many TLBs >> this flush affects, i.e. 3 in this example, so an architecture can >> sensibly decide whether it wants to use flush all or not. >> @@ -1747,7 +1748,12 @@ static bool __purge_vmap_area_lazy(unsig >> list_last_entry(&local_purge_list, >> struct vmap_area, list)->va_end); >> >> - flush_tlb_kernel_range(start, end); >> + if (tmp.va_end > tmp.va_start) >> + list_add(&tmp.list, &local_purge_list); >> + flush_tlb_kernel_vas(&local_purge_list); >> + if (tmp.va_end > tmp.va_start) >> + list_del(&tmp.list); > > So basically we end up iterating over each VA range, which seems > sensible if the range is large and we have to iterate over it page > by page. Right. > In the case you have, are "start" and "end" set on function entry > to a range, or are they set to ULONG_MAX,0 ? What I'm wondering is > whether we could get away with just having flush_tlb_kernel_vas(). > > Whether that's acceptable to others is a different question :) As I said flush_tlb_kernel_vas() should be void flush_tlb_kernel_vas(struct list_head *list, unsigned int num_entries): So that an architecture can decide whether it's worth to do walk the entries or whether it resorts to a flush all. >> +static void do_flush_vas(void *arg) >> +{ >> + struct list_head *list = arg; >> + struct vmap_area *va; >> + unsigned long addr; >> + >> + list_for_each_entry(va, list, list) { >> + /* flush range by one by one 'invlpg' */ >> + for (addr = va->va_start; addr < va->va_end; addr += PAGE_SIZE) >> + flush_tlb_one_kernel(addr); > > Isn't this just the same as: > flush_tlb_kernel_range(va->va_start, va->va_end); Indeed. Thanks, tglx