Commit a509ddeb authored by Daniel Verkamp's avatar Daniel Verkamp
Browse files

json/write: add an output buffer 

This improves output speed significantly, especially if the write
callback is expensive (e.g. issues a syscall or takes a lock).

On my test system, jsoncat citylots.json > /dev/null improves from
~2.8s to ~1.7s.

citylots.json: https://github.com/zemirco/sf-city-lots-json

 (~181 MiB)

Change-Id: I7d411ce92366712ed87ad5fc6e9b64828541db4d
Signed-off-by: default avatarDaniel Verkamp <daniel.verkamp@intel.com>
parent 21386765

lib/json/json_internal.h

+1 −0
Original line number Diff line number Diff line
@@ -47,6 +47,7 @@ 
#include <string.h>

#include <errno.h>



#include "spdk/likely.h"

#include "spdk/string.h"



#define SPDK_JSON_MAX_NESTING_DEPTH	64

lib/json/json_write.c

+58 −7
Original line number Diff line number Diff line
@@ -41,8 +41,34 @@ struct spdk_json_write_ctx { 
	bool new_indent;

	bool first_value;

	bool failed;

	size_t buf_filled;

	uint8_t buf[4096];

};



static int emit_buf_full(struct spdk_json_write_ctx *w, const void *data, size_t size);



static int

fail(struct spdk_json_write_ctx *w)

{

	w->failed = true;

	return -1;

}



static int

flush_buf(struct spdk_json_write_ctx *w)

{

	int rc;



	rc = w->write_cb(w->cb_ctx, w->buf, w->buf_filled);

	if (rc != 0) {

		return fail(w);

	}



	w->buf_filled = 0;



	return 0;

}



struct spdk_json_write_ctx *

spdk_json_write_begin(spdk_json_write_cb write_cb, void *cb_ctx, uint32_t flags)

{
@@ -60,6 +86,7 @@ spdk_json_write_begin(spdk_json_write_cb write_cb, void *cb_ctx, uint32_t flags) 
	w->new_indent = false;

	w->first_value = true;

	w->failed = false;

	w->buf_filled = 0;



	return w;

}
@@ -68,6 +95,7 @@ int 
spdk_json_write_end(struct spdk_json_write_ctx *w)

{

	bool failed;

	int rc;



	if (w == NULL) {

		return 0;
@@ -75,28 +103,51 @@ spdk_json_write_end(struct spdk_json_write_ctx *w) 


	failed = w->failed;



	rc = flush_buf(w);

	if (rc != 0) {

		failed = true;

	}



	free(w);



	return failed ? -1 : 0;

}



static int

fail(struct spdk_json_write_ctx *w)

static inline int

emit(struct spdk_json_write_ctx *w, const void *data, size_t size)

{

	w->failed = true;

	return -1;

	size_t buf_remain = sizeof(w->buf) - w->buf_filled;



	if (spdk_unlikely(size > buf_remain)) {

		/* Not enough space in buffer for the new data. */

		return emit_buf_full(w, data, size);

	}



	/* Copy the new data into buf. */

	memcpy(w->buf + w->buf_filled, data, size);

	w->buf_filled += size;

	return 0;

}



static int

emit(struct spdk_json_write_ctx *w, const void *data, size_t size)

emit_buf_full(struct spdk_json_write_ctx *w, const void *data, size_t size)

{

	size_t buf_remain = sizeof(w->buf) - w->buf_filled;

	int rc;



	rc = w->write_cb(w->cb_ctx, data, size);

	assert(size > buf_remain);



	/* Copy as much of the new data as possible into the buffer and flush it. */

	memcpy(w->buf + w->buf_filled, data, buf_remain);

	w->buf_filled += buf_remain;



	rc = flush_buf(w);

	if (rc != 0) {

		return fail(w);

	}

	return 0;



	/* Recurse to emit the rest of the data. */

	return emit(w, data + buf_remain, size - buf_remain);

}



static int