Messages in this thread Patch in this message | | | Date | Fri, 6 Apr 2001 19:07:01 +0200 | From | Andrea Arcangeli <> | Subject | Re: 2 times faster rawio and several fixes (2.4.3aa3) |
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On Fri, Apr 06, 2001 at 06:34:40PM +0200, Andrea Arcangeli wrote: > 2.4.3aa3 with rawio-1: > > root@alpha:/home/andrea > time ./rawio-bench > Opening /dev/raw1 > Allocating 50MB of memory > Reading from /dev/raw1 > Writing data to /dev/raw1 > > real 0m5.208s > user 0m0.001s > sys 0m1.162s > root@alpha:/home/andrea > time ./rawio-bench > Opening /dev/raw1 > Allocating 50MB of memory > Reading from /dev/raw1 > Writing data to /dev/raw1 > > real 0m5.233s > user 0m0.002s > sys 0m1.184s > root@alpha:/home/andrea > time ./rawio-bench > Opening /dev/raw1 > Allocating 50MB of memory > Reading from /dev/raw1 > Writing data to /dev/raw1 > > real 0m5.378s > user 0m0.002s > sys 0m1.213s > root@alpha:/home/andrea > time ./rawio-bench > Opening /dev/raw1 > Allocating 50MB of memory > Reading from /dev/raw1 > Writing data to /dev/raw1 > > real 0m5.258s > user 0m0.001s > sys 0m1.183s > root@alpha:/home/andrea >
with this patch:
--- 2.4.3aa/include/linux/iobuf.h Fri Apr 6 16:33:12 2001 +++ /misc/andrea-alpha/2.4.3aa/include/linux/iobuf.h Fri Apr 6 18:31:23 2001 @@ -24,7 +24,7 @@ * entire iovec. */ -#define KIO_MAX_ATOMIC_IO 512 /* in kb */ +#define KIO_MAX_ATOMIC_IO 1024 /* in kb */ #define KIO_STATIC_PAGES (KIO_MAX_ATOMIC_IO / (PAGE_SIZE >> 10) + 1) #define KIO_MAX_SECTORS (KIO_MAX_ATOMIC_IO * 2) applied on top of 2.4.3aa3 I get even better results:
alpha:/home/andrea # time ./rawio-bench Opening /dev/raw1 Allocating 50MB of memory Reading from /dev/raw1 Writing data to /dev/raw1
real 0m4.898s user 0m0.003s sys 0m1.138s alpha:/home/andrea # time ./rawio-bench Opening /dev/raw1 Allocating 50MB of memory Reading from /dev/raw1 Writing data to /dev/raw1
real 0m4.935s user 0m0.002s sys 0m1.159s alpha:/home/andrea # time ./rawio-bench Opening /dev/raw1 Allocating 50MB of memory Reading from /dev/raw1 Writing data to /dev/raw1
real 0m4.925s user 0m0.003s sys 0m1.162s alpha:/home/andrea # time ./rawio-bench Opening /dev/raw1 Allocating 50MB of memory Reading from /dev/raw1 Writing data to /dev/raw1
real 0m4.941s user 0m0.004s sys 0m1.166s alpha:/home/andrea #
this is most probably beacuse I'm striping on two scsi disks and this way we can send 512k requests to each disk.
NOTE: also userspace reads and writes have to be >=512kbytes in granularity or you'll generate small requests because rawio in always synchronous. And using decent sized write/reads is good idea anyways to reduce the enter/exit kernel overhead.
However we can probably stay with the 512k atomic I/O otherwise the iobuf structure will grow again of an order of 2. With 512k of atomic I/O the kiovec structure is just 8756 in size (infact probably I should allocate some of the structures dynamically instead of statics inside the kiobuf.. as it is now with my patch it's not very reliable as it needs an allocation of order 2).
BTW, some more description on the testcase: it first read 50mbytes physically contigous and then it lseek to zero and writes 50mbytes. Disk throughput in mean is 100mbyte/5sec = 20mbyte/sec.
It uses anonymous memory as in-core backend. It looks perfect testcase to me and they're the faster disks I have here around.
Here the proggy:
/* 2001 Andrea Arcangeli <andrea@suse.de> */ #include <fcntl.h> #include <unistd.h> #include <stdio.h> #include <string.h> #include <stdlib.h> #include <unistd.h> #include <sys/mman.h> #include <asm/page.h>
#define MB (1024*1024) #define BUFSIZE (50*MB)
main() { int fd, size, ret; int filemap; char * buf, * end, * tmp; printf("Opening /dev/raw1\n"); fd = open("/dev/raw1", O_RDWR); if (fd < 0) perror("open /dev/raw1"), exit(1); #if 1 printf("Allocating %dMB of memory\n", BUFSIZE/MB); buf = (char *) malloc(BUFSIZE); if (buf < 0) perror("malloc"), exit(1); end = (char *) ((unsigned long) (buf + BUFSIZE) & PAGE_MASK); buf = (char *) ((unsigned long)(buf + ~PAGE_MASK) & PAGE_MASK); #else printf("Mapping %dMB of memory\n", BUFSIZE/MB); filemap = open("deleteme", O_RDWR|O_TRUNC|O_CREAT, 0644); if (filemap < 0) perror("open"), exit(1); { int i; char buf[4096]; for (i = 0; i < BUFSIZE; i += 4096) write(filemap, &buf, 4096); } ftruncate(filemap, BUFSIZE); buf = mmap(0, BUFSIZE, PROT_READ|PROT_WRITE, MAP_SHARED, filemap, 0); if ((long) buf < 0) perror("mmap"), exit(1); if ((unsigned long) buf & ~PAGE_MASK) perror("mmap misaligned"), exit(1); end = buf + BUFSIZE; #endif size = end - buf; printf("Reading from /dev/raw1\n"); ret = read(fd, buf, size); if (ret < 0) perror("read /dev/raw1"), exit(1); if (ret != size) fprintf(stderr, "read only %d of %d bytes\n", ret, size); printf("Writing data to /dev/raw1\n"); if (lseek(fd, 0, SEEK_SET) < 0) perror("lseek"), exit(1); ret = write(fd, buf, size); if (ret < 0) perror("read /dev/raw1"), exit(1); if (ret != size) fprintf(stderr, "write only %d of %d bytes\n", ret, size); } Andrea - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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