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Make buffer shrinking algorithm a little smarter.

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svn:r4164
This commit is contained in:
Nick Mathewson 2005-05-02 22:49:24 +00:00
parent 830ac87611
commit 9c683c7613
1 changed files with 38 additions and 11 deletions
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49
src/or/buffers.c
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@ -51,6 +51,7 @@ struct buf_t {
uint32_t magic; /**< Magic cookie for debugging: Must be set to BUFFER_MAGIC */ uint32_t magic; /**< Magic cookie for debugging: Must be set to BUFFER_MAGIC */
char *mem; /**< Storage for data in the buffer */ char *mem; /**< Storage for data in the buffer */
char *cur; /**< The first byte used for storing data in the buffer. */ char *cur; /**< The first byte used for storing data in the buffer. */
size_t highwater; /**< Largest observed datalen since last buf_shrink */
size_t len; /**< Maximum amount of data that <b>mem</b> can hold. */ size_t len; /**< Maximum amount of data that <b>mem</b> can hold. */
size_t datalen; /**< Number of bytes currently in <b>mem</b>. */ size_t datalen; /**< Number of bytes currently in <b>mem</b>. */
}; };
@ -60,7 +61,8 @@ struct buf_t {
/** Size, in bytes, for minimum 'shrink' size for buffers. Buffers may start /** Size, in bytes, for minimum 'shrink' size for buffers. Buffers may start
* out smaller than this, but they will never autoshrink to less * out smaller than this, but they will never autoshrink to less
* than this size. */ * than this size. */
#define MIN_BUF_SHRINK_SIZE (16*1024) #define MIN_GREEDY_SHRINK_SIZE (16*1024)
#define MIN_LAZY_SHRINK_SIZE (4*1024)
static INLINE void peek_from_buf(char *string, size_t string_len, buf_t *buf); static INLINE void peek_from_buf(char *string, size_t string_len, buf_t *buf);
@ -212,29 +214,47 @@ static INLINE int buf_ensure_capacity(buf_t *buf, size_t capacity)
return 0; return 0;
} }
/** If the buffer is at least 2*MIN_BUF_SHRINK_SIZE bytes in capacity, /** If the buffer is at least 2*MIN_GREEDY_SHRINK_SIZE bytes in capacity,
* and if the buffer is less than 1/4 full, shrink the buffer until * and if the buffer is less than 1/8 full, shrink the buffer until
* one of the above no longer holds. (We shrink the buffer by * one of the above no longer holds. (We shrink the buffer by
* dividing by powers of 2.) * dividing by powers of 2.)
*/ */
static INLINE void buf_shrink_if_underfull(buf_t *buf) { static INLINE void buf_shrink_if_underfull(buf_t *buf) {
size_t new_len; size_t new_len;
/* If the buffer is at least .25 full, or if shrinking the buffer would /* If the buffer is at least 1/8 full, or if shrinking the buffer would
* put it under MIN_BUF_SHRINK_SIZE, don't do it. */ * put it under MIN_GREEDY_SHRINK_SIZE, don't do it. */
if (buf->datalen >= buf->len/4 || buf->len < 2*MIN_BUF_SHRINK_SIZE) if (buf->datalen >= (buf->len>>3) || buf->len < MIN_GREEDY_SHRINK_SIZE*2)
return; return;
/* Shrink new_len by powers of 2 until: datalen is at least 1/4 of /* Shrink new_len by powers of 2 until: datalen is at least 1/4 of
* new_len, OR shrinking new_len more would put it under * new_len, OR shrinking new_len more would put it under
* MIN_BUF_SHRINK_SIZE. * MIN_GREEDY_SHRINK_SIZE.
*/ */
new_len = buf->len / 2; new_len = (buf->len>>1);
while (buf->datalen < new_len/4 && new_len/2 > MIN_BUF_SHRINK_SIZE) while (buf->datalen < (new_len>>3) && new_len > MIN_GREEDY_SHRINK_SIZE*2)
new_len /= 2; new_len >>= 1;
log_fn(LOG_DEBUG,"Shrinking buffer from %d to %d bytes.", log_fn(LOG_DEBUG,"Shrinking buffer from %d to %d bytes.",
(int)buf->len, (int)new_len); (int)buf->len, (int)new_len);
buf_resize(buf, new_len); buf_resize(buf, new_len);
} }
void
buf_shrink(buf_t *buf)
{
size_t new_len;
if (buf->highwater >= (buf->len<<2) && buf->len > MIN_LAZY_SHRINK_SIZE*2)
return;
new_len = (buf->len>>1);
while (buf->highwater < (new_len>>2) && new_len > MIN_LAZY_SHRINK_SIZE*2)
new_len >>= 1;
log_fn(LOG_DEBUG,"Shrinking buffer from %d to %d bytes.",
(int)buf->len, (int)new_len);
buf_resize(buf, new_len);
buf->highwater = buf->datalen;
}
/** Remove the first <b>n</b> bytes from buf. /** Remove the first <b>n</b> bytes from buf.
*/ */
static INLINE void buf_remove_from_front(buf_t *buf, size_t n) { static INLINE void buf_remove_from_front(buf_t *buf, size_t n) {
@ -331,6 +351,8 @@ static INLINE int read_to_buf_impl(int s, size_t at_most, buf_t *buf,
return 0; return 0;
} else { /* we read some bytes */ } else { /* we read some bytes */
buf->datalen += read_result; buf->datalen += read_result;
if (buf->datalen > buf->highwater)
buf->highwater = buf->datalen;
log_fn(LOG_DEBUG,"Read %d bytes. %d on inbuf.",read_result, log_fn(LOG_DEBUG,"Read %d bytes. %d on inbuf.",read_result,
(int)buf->datalen); (int)buf->datalen);
return read_result; return read_result;
@ -397,6 +419,8 @@ read_to_buf_tls_impl(tor_tls *tls, size_t at_most, buf_t *buf, char *next)
if (r<0) if (r<0)
return r; return r;
buf->datalen += r; buf->datalen += r;
if (buf->datalen > buf->highwater)
buf->highwater = buf->datalen;
log_fn(LOG_DEBUG,"Read %d bytes. %d on inbuf; %d pending",r, log_fn(LOG_DEBUG,"Read %d bytes. %d on inbuf; %d pending",r,
(int)buf->datalen,(int)tor_tls_get_pending_bytes(tls)); (int)buf->datalen,(int)tor_tls_get_pending_bytes(tls));
return r; return r;
@ -598,6 +622,8 @@ write_to_buf(const char *string, size_t string_len, buf_t *buf)
memcpy(buf->mem, string+string_len, len2); memcpy(buf->mem, string+string_len, len2);
buf->datalen += len2; buf->datalen += len2;
} }
if (buf->datalen > buf->highwater)
buf->highwater = buf->datalen;
log_fn(LOG_DEBUG,"added %d bytes to buf (now %d total).",(int)string_len, (int)buf->datalen); log_fn(LOG_DEBUG,"added %d bytes to buf (now %d total).",(int)string_len, (int)buf->datalen);
check(); check();
return buf->datalen; return buf->datalen;
@ -1005,7 +1031,8 @@ void assert_buf_ok(buf_t *buf)
tor_assert(buf); tor_assert(buf);
tor_assert(buf->magic == BUFFER_MAGIC); tor_assert(buf->magic == BUFFER_MAGIC);
tor_assert(buf->mem); tor_assert(buf->mem);
tor_assert(buf->datalen <= buf->len); tor_assert(buf->highwater <= buf->len);
tor_assert(buf->datalen <= buf->highwater);
#ifdef SENTINELS #ifdef SENTINELS
{ {
uint32_t u32 = get_uint32(buf->mem - 4); uint32_t u32 = get_uint32(buf->mem - 4);