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charset=us-ascii Content-Disposition: inline In-Reply-To: <87a5y5a6kj.ffs@tglx> X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 4CFBD40009 X-Stat-Signature: b9973rtijo31tdbem3zoixyabgiidjsm X-HE-Tag: 1684169958-828361 X-HE-Meta: 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 o1J1Q/qh 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, 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 06:43:40PM +0200, Thomas Gleixner wrote: > 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, you asked the architecture to flush a large range, and are then surprised if it takes a long time. There is no way to know how many of those are useful. Now, while using the sledge hammer of flushing all TLB entries may sound like a good answer, if we're only evicting 31 entries, the other entries are probably useful to have, no? I think that you'd only run into this if you had a huge BPF program and you tore it down, no? -- RMK's Patch system: https://www.armlinux.org.uk/developer/patches/ FTTP is here! 80Mbps down 10Mbps up. Decent connectivity at last!