Date: Thu, 15 Nov 2012 11:09:48 -0800 From: Adrian Chadd <adrian@freebsd.org> To: Alan Cox <alc@rice.edu> Cc: "Jayachandran C." <jchandra@freebsd.org>, mips@freebsd.org Subject: Re: ZERO_REGION_SIZE Message-ID: <CAJ-Vmon-v3K7012ti_L6ao3wQHfQ99Jau1kJ%2BGhumbPjAuSDww@mail.gmail.com> In-Reply-To: <50A53391.4080909@rice.edu> References: <50A53391.4080909@rice.edu>
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Alan, would you like me to send you some MIPS hardwarE? Adrian On 15 November 2012 10:25, Alan Cox <alc@rice.edu> wrote: > Given the possibility of L1 cache aliasing on some (many?) MIPS > processors, I think that you, i.e., MIPS users, should evaluate the > performance effects of the following change: > > Index: mips/include/vmparam.h > =================================================================== > --- mips/include/vmparam.h (revision 243091) > +++ mips/include/vmparam.h (working copy) > @@ -190,6 +190,6 @@ > */ > #define VM_NFREEORDER 9 > > -#define ZERO_REGION_SIZE (64 * 1024) /* 64KB */ > +#define ZERO_REGION_SIZE 4096 > > #endif /* !_MACHINE_VMPARAM_H_ */ > > You can quantify the impact with a simple test like: > > dd if=/dev/zero of=/dev/null bs=<64 or 128>k count=<something non-trivial> > > If possible, please use a kernel without WITNESS or INVARIANTS. > > Alan > > P.S. I would also be curious how setting this to 8192 would perform. >
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