diff options
Diffstat (limited to 'include/haproxy/dynbuf-t.h')
| -rw-r--r-- | include/haproxy/dynbuf-t.h | 73 |
1 files changed, 73 insertions, 0 deletions
diff --git a/include/haproxy/dynbuf-t.h b/include/haproxy/dynbuf-t.h index b5545ab..f0ca187 100644 --- a/include/haproxy/dynbuf-t.h +++ b/include/haproxy/dynbuf-t.h @@ -22,6 +22,79 @@ #ifndef _HAPROXY_DYNBUF_T_H #define _HAPROXY_DYNBUF_T_H +#include <haproxy/list-t.h> + +/* Describe the levels of criticality of each allocation based on the expected + * use case. We distinguish multiple use cases, from the least important to the + * most important one: + * - allocate a buffer to grow a non-empty ring: this should be avoided when + * resources are becoming scarce. + * - allocate a buffer for very unlikely situations (e.g. L7 retries, early + * data). These may acceptably fail on low resources. + * - buffer used to receive data in the mux at the connection level. Please + * note that this level might later be resplit into two levels, one for + * initial data such as a new request, which may be rejected and postponed, + * and one for data continuation, which may be needed to complete a request + * or receive some control data allowing another buffer to be flushed. + * - buffer used to produce data at the endpoint for internal consumption, + * typically mux streams and applets. These buffers will be allocated until + * a channel picks them. Not processing them might sometimes lead to a mux + * being clogged and blocking other streams from progressing. + * - channel buffer: this one may be allocated to perform a synchronous recv, + * or just preparing for the possibility of an instant response. The + * response channel always allocates a buffer when entering process_stream, + * which is immediately released if unused when leaving. + * - buffer used by the mux sending side, often allocated by the mux's + * snd_buf() handler to encode the outgoing channel's data. + * - buffer permanently allocated at boot (e.g. temporary compression + * buffers). If these fail, we can't boot. + * + * Please DO NOT CHANGE THESE LEVELS without first getting a full understanding + * of how all this works and touching the DB_F_CRIT_MASK and DB_CRIT_TO_QUEUE() + * macros below! + */ +enum dynbuf_crit { + DB_GROW_RING = 0, // used to grow an existing buffer ring + DB_UNLIKELY, // unlikely to be needed (e.g. L7 retries) + /* The 4 levels below are subject to queueing */ + DB_MUX_RX, // buffer used to store incoming data from the system + DB_SE_RX, // buffer used to store incoming data for the channel + DB_CHANNEL, // buffer used by the channel for synchronous reads + DB_MUX_TX, // buffer used to store outgoing mux data + /* The one below may never fail */ + DB_PERMANENT, // buffers permanently allocated. +}; + +/* The values above are expected to be passed to b_alloc(). In addition, some + * Extra flags can be passed by oring the crit value above with one of these + * high-bit flags. + */ +#define DB_F_NOQUEUE 0x80000000U // ignore presence of others in queue +#define DB_F_CRIT_MASK 0x000000FFU // mask to keep the criticality bits + + +/* We'll deal with 4 queues, with indexes numbered from 0 to 3 based on the + * criticality of the allocation. All criticality levels are mapped to a 2-bit + * queue index. While some levels never use the queue (the first two), some of + * the others will share a same queue, and all levels will define a ratio of + * allocated emergency buffers below which we refrain from trying to allocate. + * In practice, for now the thresholds will just be the queue number times 33% + * so that queue 0 is allowed to deplete emergency buffers and queue 3 not at + * all. This gives us: queue idx=3 for DB_MUX_RX and below, 2 for DB_SE_RX, + * 1 for DB_CHANNEL, 0 for DB_MUX_TX and above. This must match the DYNBUF_NBQ + * in tinfo-t.h. + */ + +#define DB_CRIT_TO_QUEUE(crit) ((0x000001BF >> ((crit) * 2)) & 3) + +#define DB_GROW_RING_Q DB_CRIT_TO_QUEUE(DB_GROW_RING) +#define DB_UNLIKELY_Q DB_CRIT_TO_QUEUE(DB_UNLIKELY) +#define DB_MUX_RX_Q DB_CRIT_TO_QUEUE(DB_MUX_RX) +#define DB_SE_RX_Q DB_CRIT_TO_QUEUE(DB_SE_RX) +#define DB_CHANNEL_Q DB_CRIT_TO_QUEUE(DB_CHANNEL) +#define DB_MUX_TX_Q DB_CRIT_TO_QUEUE(DB_MUX_TX) +#define DB_PERMANENT_Q DB_CRIT_TO_QUEUE(DB_PERMANENT) + /* an element of the <buffer_wq> list. It represents an object that need to * acquire a buffer to continue its process. */ |