Date: Wed, 4 Mar 2020 17:21:53 -0500 From: Mark Johnston <markj@freebsd.org> To: Eric Joyner <erj@erj.cc> Cc: src-committers <src-committers@freebsd.org>, svn-src-all <svn-src-all@freebsd.org>, svn-src-head <svn-src-head@freebsd.org> Subject: Re: svn commit: r358432 - in head/sys: kern sys vm Message-ID: <20200304222153.GA58468@raichu> In-Reply-To: <CAKdFRZi9g=tRArTXGaUV0kszOR%2BMZhrFFmZS3m=pWcZZC08nwQ@mail.gmail.com> References: <202002281605.01SG5Iox077824@repo.freebsd.org> <CAKdFRZi9g=tRArTXGaUV0kszOR%2BMZhrFFmZS3m=pWcZZC08nwQ@mail.gmail.com>
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On Wed, Mar 04, 2020 at 01:15:59PM -0800, Eric Joyner wrote: > Hi Mark, > > Is the addition of #include <sys/_bitcount.h> in sys/sys/refcount.h > actually necessary? I don't see anything in there used in refcount.h, and > the kernel appears to compile without it, at least on amd64. No, it is left over from an earlier iteration of the patch. I will remove it. Thanks. > On Fri, Feb 28, 2020 at 8:05 AM Mark Johnston <markj@freebsd.org> wrote: > > > Author: markj > > Date: Fri Feb 28 16:05:18 2020 > > New Revision: 358432 > > URL: https://svnweb.freebsd.org/changeset/base/358432 > > > > Log: > > Add a blocking counter KPI. > > > > refcount(9) was recently extended to support waiting on a refcount to > > drop to zero, as this was needed for a lockless VM object > > paging-in-progress counter. However, this adds overhead to all uses of > > refcount(9) and doesn't really match traditional refcounting semantics: > > once a counter has dropped to zero, the protected object may be freed at > > any point and it is not safe to dereference the counter. > > > > This change removes that extension and instead adds a new set of KPIs, > > blockcount_*, for use by VM object PIP and busy.
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