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[PATCH 2/6] libpager: Do not flush in-core pages on offer


From: Sergey Bugaev
Subject: [PATCH 2/6] libpager: Do not flush in-core pages on offer
Date: Thu, 6 May 2021 15:56:27 +0300

pager_offer_page () is documented to may ignore the offered page if
the kernel already has a copy in core (indeed, that's what Mach does).

However the current behavior is the inverse of that: it asks the kernel
to flush (i.e. drop) its in-core copy, and replace it with the offered
one. Fix this by not doing that, and calling memory_object_data_supply ()
directly.
---
 libpager/offer-page.c | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/libpager/offer-page.c b/libpager/offer-page.c
index ddea236a..0b0ca2eb 100644
--- a/libpager/offer-page.c
+++ b/libpager/offer-page.c
@@ -34,13 +34,6 @@ pager_offer_page (struct pager *p,
     goto release_out;
 
   short *pm_entry = &p->pagemap[offset / vm_page_size];
-
-  while (*pm_entry & PM_INCORE)
-    {
-      pthread_mutex_unlock (&p->interlock);
-      pager_flush_some (p, offset, vm_page_size, 1);
-      pthread_mutex_lock (&p->interlock);
-    }
   *pm_entry |= PM_INCORE;
 
   memory_object_data_supply (p->memobjcntl, offset, buf, vm_page_size, 0,
-- 
2.31.1




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