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Subject: [Bug 223059] [patch] consider skipped 2 pages in sw_nblks and add
 size check before blist_alloc
Date: Thu, 19 Oct 2017 06:08:32 +0000
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D223059

--- Comment #1 from Alan Cox <alc@FreeBSD.org> ---
Testing "(sp->sw_nblks - sp->sw_used >=3D npages)" before every call to
blist_alloc() is of no real benefit.  In the common case, where there is
available swap space, it is added overhead, albeit a tiny amount of overhea=
d.=20
Only in the rare case, where there is no swap space available will it be of=
 any
benefit.  But, in that case, the gain is minimal.  The hinting mechanism in=
 the
blist code will quickly conclude that there is no available space, and retu=
rn
failure.  In summary, the tiny amount of overhead in the common case is goi=
ng
to outweigh the gain in the rare case.

--=20
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