On 02/03/2026 23:42, Roland Mainz via Cygwin wrote:
Hi!
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Quick note (mainly for Corinna):
Cygwin 3.7.0, I noticed a possible performance improvement while
working on ms-nfs41-client:
For each file/dir listed by /usr/bin/find, rm -Rf .. etc I see two
QueryVolumeInformation (volumequery class=1 and class=4) which
technically could be cached per mount+process.
I also recall an old confcall at SUN around |openat(dirfd, ...)|,
technically this info could also be cached per-dirfd (and inherited if
the dirfd is used to |openat()| another dir fd), making such a cache
last longer...
The hard part of this is to quickly (without slowing down the total)
detect if a subdirectory is a mountpoint for some other location
(possibly within the same file system, yes windows has had the equivalent
of bind mounts ever since the MSDOS added the JOIN command).
Similarly, find --xdev etc. should stop at such subdir mounts that don't
change st_dev (kernel/cygwin1 changes that assign virtual IDs to each bind
mount don't work as they would hurt other uses of st_dev).
A more practical way until POSIX agrees on a solution is for cygwin to
keep an in-process cache per "volume serial number" from the
GetFileInformaionByHandle() equivalant of fstat()
Enjoy
Jakob
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Jakob Bohm, CIO, Partner, WiseMo A/S. https://www.wisemo.com
Transformervej 29, 2860 Søborg, Denmark. Direct +45 31 13 16 10
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