Messages in this thread | | | Date | Wed, 11 Dec 2002 19:21:10 -0500 | From | "Patrick R. McManus" <> | Subject | Re: Memory Measurements and Lots of Files and Inodes |
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[Andrew Morton: Dec 11 16:09] > "Patrick R. McManus" wrote: > > > > ... > > Just sitting back and watching vmstat while this runs my 'free' memory > > drops from ~600MB to about ~16MB.. the buffers and cache remain roughly > > constant.. at 16MB some sort of garbage collection kicks in - there is > > a notable system pause and ~70MB moves from the used to the 'free' > > column... this process repeats more or less in a steady state. > > Probably `negative dentries' - cached directory entries which say > "this file isn't there" so we don't need to go into the fs to > find that out. > > If you could share your test apps that would help a lot.
sure! this is the "lots of files" program.
#include <stdio.h> #include <sys/types.h> #include <sys/stat.h> #include <fcntl.h>
#define BSZ 2000 unsigned char buf[BSZ+256];
main () { int fd,i,j; unsigned int ctr=0; unsigned char r=0; char f1[32],f2[32],f3[32],f4[32]; while (1) { sprintf (f1,"fxa_%06d",ctr++); sprintf (f2,"fxa_%06d",ctr++); sprintf (f3,"fxa_%06d",ctr++); sprintf (f4,"fxa_%06d",ctr++);
fd = open (f1,O_CREAT | O_RDWR); memset (buf,r++,BSZ+256); write (fd,buf,BSZ+r); close (fd); fd = open (f2,O_CREAT | O_RDWR); memset (buf,r++,BSZ+256); write (fd,buf,BSZ+r); close (fd); fd = open (f3,O_CREAT | O_RDWR); memset (buf,r++,BSZ+256); write (fd,buf,BSZ+r); close (fd); fd = open (f4,O_CREAT | O_RDWR); memset (buf,r++,BSZ+256); write (fd,buf,BSZ+r); close (fd); unlink (f1); unlink (f2); unlink (f3); unlink (f4); if (!r) fprintf (stdout,".");fflush (stdout); } }
and this is the "gimme 300MB even though free sez I hardly have anything" program:
#define BS (30*1024*1024) main() { char *x; x = malloc (BS); if (!x) printf ("heh - x is NULL\n"); else { printf ("allocd\n"); memset (x,0x31,BS); printf ("set\n"); free (x); printf ("freed\n"); } }
> On your machine it'll be "all of swap plus all of physical memory > minus whatever malloc'ed memory you're using now minus 8-12 megabytes". > There isn't much memory which cannot be reclaimed unless you have a > huge machine or you're doing odd things.
this is useful advice, thanks. Basically what the new procps does? - 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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