I read my MH mail from two clients: Emacs MH mode, directly from the MH
dirs, and Mozilla via the UW IMAP server. The IMAP server frequently
re-reads my mailboxes, which are sometimes large (e.g. 4k, 6k messages),
and it was taking a long time. I found that the routine mh_headers
always reads the entire message no matter how long it is and always does
strcrlfcpy on the entire body, while I certainly won't be requesting all
the bodies in the client. I felt it is doing unnecessary work, both I/O
and CPU.
I made a change so that mh_headers reads only the beginning of each
message file in 4kb chunks until it reaches the end of headers. I
reorganized the code a bit, to avoid duplication between mh_headers and
mh_text which requires both headers and body. Empirically, there tends
to be not more than 3kb of headers in my messages, so 4kb seems like a
good compromise. I didn't make it configurable, just hardcoded 4096.
After the change, folder scan time for 6k messages went down from 20+s
to ~13s on a dual CPU Sunblade-2500 running Solaris 8, with Mozilla
1.7.3 and imapd running on the same machine. Everything seems to work. I
verified with debug logging that I actually do go through the
header-only branch.
diff -c patch attached. Please feel free to adjust as necessary.
--Michael Klepikov
*** imap-2004c1.klm/src/osdep/unix/mh.c Thu Mar 24 15:43:50 2005
--- imap-2004c1/src/osdep/unix/mh.c Thu Mar 24 15:12:49 2005
***
*** 565,580
if (mail_elt (stream,i)-sequence) mh_header (stream,i,j,NIL);
}
! /* MH mail fetch message header
* Accepts: MAIL stream
*message # to fetch
*pointer to returned header text length
*option flags
* Returns: message header in RFC822 format
*/
! char *mh_header (MAILSTREAM *stream,unsigned long msgno,unsigned long *length,
!long flags)
{
unsigned long i,hdrsize;
int fd;
--- 565,581
if (mail_elt (stream,i)-sequence) mh_header (stream,i,j,NIL);
}
! /* MH mail fetch message header and (optionally) text
* Accepts: MAIL stream
*message # to fetch
*pointer to returned header text length
*option flags
+ * a boolean flag whether or not need msg text
* Returns: message header in RFC822 format
*/
! char *mh_msg_fetch (MAILSTREAM *stream,unsigned long msgno,
! unsigned long *length, long flags, int need_text)
{
unsigned long i,hdrsize;
int fd;
***
*** 585,591
*length = 0;/* default to empty */
if (flags FT_UID) return ;/* UID call impossible */
elt = mail_elt (stream,msgno);/* get elt */
! if (!elt-private.msg.header.text.data) {
/* purge cache if too big */
if (LOCAL-cachedtexts max (stream-nmsgs * 4096,2097152)) {
mail_gc (stream,GC_TEXTS);/* just can't keep that much */
--- 586,593
*length = 0;/* default to empty */
if (flags FT_UID) return ;/* UID call impossible */
elt = mail_elt (stream,msgno);/* get elt */
! if (!elt-private.msg.header.text.data ||
! (need_text !elt-private.msg.text.text.data)) {
/* purge cache if too big */
if (LOCAL-cachedtexts max (stream-nmsgs * 4096,2097152)) {
mail_gc (stream,GC_TEXTS);/* just can't keep that much */
***
*** 608,634
LOCAL-buf = (char *) fs_get ((LOCAL-buflen = sbuf.st_size) + 1);
}
/* slurp message */
! read (fd,LOCAL-buf,sbuf.st_size);
/* tie off file */
! LOCAL-buf[sbuf.st_size] = '\0';
! close (fd); /* flush message file */
/* find end of header */
! for (i = 0,t = LOCAL-buf; *t !(i (*t == '\n')); i = (*t++ ==
'\n'));
/* number of header bytes */
! hdrsize = (*t ? ++t : t) - LOCAL-buf;
! elt-rfc822_size =/* size of entire message in CRLF form
*/
! (elt-private.msg.header.text.size =
!strcrlfcpy (elt-private.msg.header.text.data,i,LOCAL-buf,
! hdrsize)) +
!(elt-private.msg.text.text.size =
! strcrlfcpy (elt-private.msg.text.text.data,i,t,
! sbuf.st_size - hdrsize));
/* add to cached size */
! LOCAL-cachedtexts += elt-rfc822_size;
}
*length = elt-private.msg.header.text.size;
return (char *) elt-private.msg.header.text.data;
}
/* MH mail fetch message text (body only)
* Accepts: MAIL stream
--- 610,680
LOCAL-buf = (char *) fs_get ((LOCAL-buflen = sbuf.st_size) + 1);
}
/* slurp message */
! if (need_text) {
! /*syslog (LOG_ALERT,Fetching msg with text #%ld, msgno);*/
! read (fd,LOCAL-buf,sbuf.st_size);
