Question

I left a record processing program of mine running for a few minutes under strace.

This showed in those minutes over 200 000 000 calls to stat("/etc/localtime",..) which sounds a bit excessive and unneeded.

The strace output looks like this:

write(1, "C137015 393393093052629137110 47"..., 16384) = 16384
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
stat("/etc/localtime", {st_mode=S_IFREG|0644, st_size=2225, ...}) = 0
read(0, "\224q\1\207\0\0\202\1\4\203\1\4\204\1\1\205\1\1\206\1\7\207\1\6\211\1\22\212\1\22\213\1"..., 16384) = 16384

Essentially it turned out to be 1 stat() call for every record processed and the culprit turned out to be this quite ordinary line of code

strftime(call->date_time,DATELEN,"%Y%m%d %H%M%S",&tm_buf);

So – how can I avoid strftime() calling stat(/etc/localtime) at every call?

Answer 1

It might be doing that because your timezone isn’t set. strftime queries /etc/localtime to find it.

Try setting the TZ environment variable.

Here’s a link for that behavior.