Date: Fri, 3 Jan 2003 15:22:59 +0200 From: Dimitar Peikov <mitko@rila.bg> To: freebsd-hackers@freebsd.org Subject: Re: bzero() in mfs_doio() Message-ID: <200301031522.59212.mitko@rila.bg> In-Reply-To: <200301031519.22540.mitko@rila.bg> References: <200301031519.22540.mitko@rila.bg>
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Upps, sorry, too much wine during the holidays. I've not read the code
correctly ;-(
On Friday 03 January 2003 15:19, Dimitar Peikov wrote:
> Hi,
>
> I've read some part of the UFS/MFS code and saw the bzero() in code, bu=
t
> according the madvice() manual page for MADV_FREE, this step is not nee=
ded.
> Also frequent calls to mfs_doio() causes serious performance penalty, a=
m I
> right?
>
>
>
> MADV_FREE Gives the VM system the freedom to free pages, an=
d
> tells the system that information in the specified page range is no lon=
ger
> important. This is an efficient way of allowing malloc(3) to free page=
s
> 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.=20
> 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 modif=
ied
> again.
>
>
>
> /sys/ufs/mfs/mfs_vnops.c:259
>
> =09=09=09bytes &=3D ~PAGE_MASK;
> =09=09=09if (bytes !=3D 0) {
> =09=09=09=09bzero(&uap, sizeof(uap));
> =09=09=09=09uap.addr =3D base;
> =09=09=09=09uap.len =3D bytes;
> =09=09=09=09uap.behav =3D MADV_FREE;
> =09=09=09=09madvise(curproc, &uap);
> =09=09=09}
- --=20
Dimitar Peikov
Programmer Analyst
Globalization Group
"We Build e-Business" =20
RILA Solutions =20
27 Building, Acad.G.Bonchev Str. =20
1113 Sofia, Bulgaria =20
phone: (+359 2) 9797320=20
phone: (+359 2) 9797300=20
fax: (+359 2) 9733355 =20
http://www.rila.com=20
GnuPG key http://earth.rila.bg/~mitko/mitko.key.asc
GnuPG key http://www.bgzone.com/~mitko/mitko.key.asc
Key fingerprint 97AF 6192 78E2 AC68 FD56 CCB0 68B9 DF7D B3C1 9ED7
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