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sh: Don't allocate a redirtab if there are no redirections.

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Builtins (including variable assignments without command word), function
calls and redirected compound commands need to restore file descriptors
to their original state after execution. This is handled by allocating a
redirtab structure. These mallocs and frees show up heavily in pmcstat.

Only allocate a redirtab if there are actually redirections and maintain a
count of how many levels of REDIR_PUSH there are without redirtabs.

A simple loop without external programs like

sh -c 'i=0; w=$(printf %0100d 7); while [ "$i" -lt 1000000 ]; do
    i=$((i+1)); done'

is over 25% faster on an amd64 bhyve VM.
This commit is contained in:
Jilles Tjoelker 2016-01-30 21:21:25 +00:00
parent 7b6779b66b
commit bd9b38d1f7
1 changed files with 22 additions and 7 deletions
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29
bin/sh/redir.c
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@ -70,6 +70,7 @@ struct redirtab {
struct redirtab *next;
int renamed[10];
int fd0_redirected;
unsigned int empty_redirs;
};
@ -82,6 +83,9 @@ static struct redirtab *redirlist;
*/
static int fd0_redirected = 0;
/* Number of redirtabs that have not been allocated. */
static unsigned int empty_redirs = 0;
static void openredirect(union node *, char[10 ]);
static int openhere(union node *);
@ -115,12 +119,17 @@ redirect(union node *redir, int flags)
memory[i] = 0;
memory[1] = flags & REDIR_BACKQ;
if (flags & REDIR_PUSH) {
sv = ckmalloc(sizeof (struct redirtab));
for (i = 0 ; i < 10 ; i++)
sv->renamed[i] = EMPTY;
sv->fd0_redirected = fd0_redirected;
sv->next = redirlist;
redirlist = sv;
empty_redirs++;
if (redir != NULL) {
sv = ckmalloc(sizeof (struct redirtab));
for (i = 0 ; i < 10 ; i++)
sv->renamed[i] = EMPTY;
sv->fd0_redirected = fd0_redirected;
sv->empty_redirs = empty_redirs - 1;
sv->next = redirlist;
redirlist = sv;
empty_redirs = 0;
}
}
for (n = redir ; n ; n = n->nfile.next) {
fd = n->nfile.fd;
@ -303,6 +312,12 @@ popredir(void)
struct redirtab *rp = redirlist;
int i;
INTOFF;
if (empty_redirs > 0) {
empty_redirs--;
INTON;
return;
}
for (i = 0 ; i < 10 ; i++) {
if (rp->renamed[i] != EMPTY) {
if (rp->renamed[i] >= 0) {
@ -313,8 +328,8 @@ popredir(void)
}
}
}
INTOFF;
fd0_redirected = rp->fd0_redirected;
empty_redirs = rp->empty_redirs;
redirlist = rp->next;
ckfree(rp);
INTON;