Date: Fri, 3 Jan 2003 15:19:19 +0200 From: Dimitar Peikov <mitko@rila.bg> To: freebsd-hackers@freebsd.org Subject: bzero() in mfs_doio() Message-ID: <200301031519.22540.mitko@rila.bg>
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Hi,
I've read some part of the UFS/MFS code and saw the bzero() in code, but
according the madvice() manual page for MADV_FREE, this step is not needed.
Also frequent calls to mfs_doio() causes serious performance penalty, am I
right?
>>>>>>
MADV_FREE Gives the VM system the freedom to free pages, and tells
the system that information in the specified page range
is no longer important. This is an efficient way of
allowing malloc(3) to free pages anywhere in the address
space, while keeping the address space valid. The next
time that the page is referenced, the page might be
demand zeroed, or might contain the data that was there
before the MADV_FREE call. References made to that
address space range will not make the VM system page the
information back in from backing store until the page is
modified again.
>>>>>>
/sys/ufs/mfs/mfs_vnops.c:259
>>>>>>
bytes &= ~PAGE_MASK;
if (bytes != 0) {
bzero(&uap, sizeof(uap));
uap.addr = base;
uap.len = bytes;
uap.behav = MADV_FREE;
madvise(curproc, &uap);
}
>>>>>>
- --
Dimitar Peikov
Programmer Analyst
Globalization Group
"We Build e-Business"
RILA Solutions
27 Building, Acad.G.Bonchev Str.
1113 Sofia, Bulgaria
phone: (+359 2) 9797320
phone: (+359 2) 9797300
fax: (+359 2) 9733355
http://www.rila.com
GnuPG key http://earth.rila.bg/~mitko/mitko.key.asc
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