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Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-kernel@vger.kernel.org, Lance Yang References: <20260818134934.92354-1-leon.hwang@linux.dev> Content-Language: en-US From: Leon Hwang In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: E03CC1C0002 X-Stat-Signature: 3ipwka38mx8wndjrttix9iq8xa4f3xk8 X-Rspam-User: X-HE-Tag: 1787104522-620517 X-HE-Meta: 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 atrDXdUX rdnMgGyJzyF6fdUdTzKL1jr4Y5y58jdQz4L7HRHanltkYPkXb2/g7k+PJoUBhO+33qBmvXZ82aNgua0OWEzw2EXB/w6eF0a13UGT1c9vU4aqHgPbPdjd0SqluO/t2zDwOngw+YusXoU8d4KIAsgXUmYgPBFeQaPoXar6khFXrOCt5EXW87Fz33FlRzJE9tsyLJaje4oXci3cMCt0Ur4EYSbtc7do/x73fc+a4788C0XFKVJ6PhFkN9yiwPb9wa6LWkFXVYTkPyfjU19ANaeYYvJ4I2/bEHyjqudPZosFvN38FRZKEOHsaIFntmGnH0u6jaEid Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 18/8/26 22:09, Mike Rapoport wrote: > On Tue, Aug 18, 2026 at 09:49:34PM +0800, Leon Hwang wrote: >> Packet receive timeouts were seen in production. Tracing showed that an >> exiting process with a sparse 2.5 TiB mapping could remain in kernel >> context for over 20 ms without reaching a scheduling point while >> freeing PTE page-table pages. Hard IRQs could still be handled, but the >> per-CPU ksoftirqd thread and other runnable tasks could not run during >> that interval, delaying NET_RX softirq work queued to ksoftirqd. >> >> Like zap_pud_range(), add cond_resched() to free_pud_range() so >> ksoftirqd and other runnable tasks can run between PUD entries. Testing >> with PREEMPT_NONE showed that the maximum interval between scheduling >> points fell from over 20 ms to below 2 ms. >> >> Reported-by: Lance Yang >> Tested-by: Lance Yang >> Signed-off-by: Leon Hwang >> --- >> mm/memory.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/memory.c b/mm/memory.c >> index 4134ac607ee0..68c15449de07 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -231,7 +231,7 @@ static inline void free_pud_range(struct mmu_gather *tlb, p4d_t *p4d, >> if (pud_none_or_clear_bad(pud)) >> continue; >> free_pmd_range(tlb, pud, addr, next, floor, ceiling); >> - } while (pud++, addr = next, addr != end); >> + } while (pud++, cond_resched(), addr = next, addr != end); > > This is really obscure, can't it be in the loop body? Agreed. It should be in the loop body, after free_pmd_range(). Thanks, Leon >> >> start &= P4D_MASK; >> if (start < floor) >> -- >> 2.55.0 >> >> >