if a single process is performing a large number of requests (in this
case writing a large file). The writing process could monopolise the
recieve lock and prevent any other processes from recieving their
replies.
It also adds a new sysctl variable 'vfs.nfs.dwrite' which controls the
behaviour which originally pointed out the problem. When a process
writes to a file over NFS, it usually arranges for another process
(the 'iod') to perform the request. If no iods are available, then it
turns the write into a 'delayed write' which is later picked up by the
next iod to do a write request for that file. This can cause that
particular iod to do a disproportionate number of requests from a
single process which can harm performance on some NFS servers. The
alternative is to perform the write synchronously in the context of
the original writing process if no iod is avaiable for asynchronous
writing.
The 'delayed write' behaviour is selected when vfs.nfs.dwrite=1 and
the non-delayed behaviour is selected when vfs.nfs.dwrite=0. The
default is vfs.nfs.dwrite=1; if many people tell me that performance
is better if vfs.nfs.dwrite=0 then I will change the default.
Submitted by: Hidetoshi Shimokawa <simokawa@sat.t.u-tokyo.ac.jp>
parse.c(1.9) was:
revision 1.9
date: 1996/09/12 03:03:25; author: bde; state: Exp; lines: +7 -6
Fixed handling of `!=' assignment. Don't warn if the shell's output is
null, but warn if there was an error reading it.
Suggested by: Bruce Evans <bde@zeta.org.au>
opened. After that, the directories are already present, and there is
no point in adding them again. This doesn't fix any bugs; it's just for
efficiency.
features are used without testing for i586 features that they depend
on. Configuring option PERFMON without configuring a suitable cpu
still doesn't fail right.
(1) Merged i386/i386/sb.h, deleted pc98/pc98/sb.h.
(2) pc98/conf/GENERIC8 looks more like i386/conf/GENERIC now.
(3) Fixed display bug in pc98/boot/biosboot/io.c.
(4) Prepare to merge memory allocation routines:
pc98/i386/locore.s
pc98/i386/machdep.c
pc98/pc98/pc98_machdep.c
pc98/pc98/pc98_machdep.h
(5) Support new board "C-NET(98)":
pc98/pc98/if_ed98.h
pc98/pc98/if_ed.c
(6) Make sure FPU is recognized for non-Intel CPUs:
pc98/pc98/npx.c
(7) Do not expect bss to be zero-allocated:
pc98/pc98/pc98.c
Submitted by: The FreeBSD(98) Development Team
Also disabled -Wunused. It caused too many warnings even for me.
The sign mismatch warnings should be fixed first. They are more
important and harder to disable (they are controlled by -W, which
controls too many things).
I586_OPTIMIZED_BCOPY is configured.
Similarly for bzero/I586_OPTIMIZED_BZERO.
Fake 586's had better have a hardware FPU with non-broken exception
handling (we mask exceptions, but broken exception handling may trap
on the instructions that do the masking). I guess this means that
the routines won't work on most 386's or FPUless 486's even when they
have a h/w FPU.
These are based on using the FPU to do 64-bit stores. They also
use i586-optimized instruction ordering, i586-optimized cache
management and a couple of other tricks. They should work on any
i*86 with a h/w FPU, but are slower on at least i386's and i486's.
They come close to saturating the memory bus on i586's. bzero()
can maintain a 3-3-3-3 burst cycle to 66 MHz non-EDO main memory
on a P133 (but is too slow to keep up with a 2-2-2-2 burst cycle
for EDO - someone with EDO should fix this). bcopy() is several
cycles short of keeping up with a 3-3-3-3 cycle for writing. For
a P133 writing to 66 MHz main memory, it just manages an N-3-3-3,
3-3-3-3 pair of burst cycles, where N is typically 6.
The new routines are not used by default. They are always configured
and can be enabled at runtime using a debugger or an lkm to change
their function pointer, or at compile time using new options (see
another log message).
Removed old, dead i586_bzero() and i686_bzero(). Read-before-write is
usually bad for i586's. It doubles the memory traffic unless the data
is already cached, and data is (or should be) very rarely cached for
large bzero()s (the system should prefer uncached pages for cleaning),
and the amount of data handled by small bzero()s is relatively small
in the kernel.
Improved comments about overlapping copies.
Removed unused #include.
